You want to be ready for characters being creative in combat. The Battle Master Fighter archetype has a few maneuvers which I think are techniques that anyone engaged in melee combat should be able to try: parrying, disarming, tripping. Also, I think there should be mechanics for a charging attack - there is the Charger Feat, but I feel it should be a combat option for all characters. This is how I would play them:

Parrying would be used as a reaction, but would take up one of a character's attacks. The character rolls an attack roll vs the roll of any successful attack made against them. If they score the same or higher, they parry the blow. They roll damage to see how much they reduce the damage of the strike made against them.

Disarming would be an attack roll made at Disadvantage and the target makes a Strength or Dexterity saving throw vs the roll of a successful strike.

Tripping would work the same as shoving an opponent into the prone position, as described in the PBH.

 Charging is a little trickier and I haven't quite figured it out. I'm thinking it will work somewhere between the Charger Feat and a Barbarian's reckless attack. Any suggestions? Or thoughts on the other maneuvers?

I like the All-Out Attack mechanic from GURPS, where you give up your defenses for one round to increase your offensive capabilities, so here's the D&D 5e version:

All-Out Attack.  When you take the Attack action on your turn, you can choose to forgo your defenses to put more effort into your attacks.  When you do so, your attacks have advantage until the end of your turn, but attacks against you automatically hit until the start of your next turn and you automatically fail all Strength and Dexterity saving throws until the start of your next turn. 

I agree in principle that there should be more combat options in 5e, however you're suggestions wouldn't really be workable.  

Parrying is largely built into your AC, and having a separate opposed roll just slows down combat.  Also, there is no mechanism in 5e to give up one attack.  The closest would be readying an action to parry, which would give up all your attacks.  This is also essentially what happens when you use the Dodge action.  Since a reaction doesn't occur on your turn, you would have to not use one attack in the hope that you would be attacked later and could parry, potentially just wasting it if you were not attacked that round, or were attacked with a spell or at range instead.  

Disarm: Attacking with disadvantage followed by a saving throw means you would rarely be successful.  There are rules for disarming in the DMG.  I agree they should be in the PHB.

Trip: Shoving someone prone is a trip, nothing needed there.

Charge: Unless you have a reach weapon or are mounted, charging a trained warrior is more likely to get you killed than them.  It telegraphs your attack and has little benefit.  There is no need for it beyond the feat.

Sorry if I'm being kind of harsh.

It's not harsh - I expected such a response. Thing is, players want to be creative rather than always just saying, "I'll attack," and you want to give them a chance for success, so looking for any other suggestions. 

I can see how you would say that parrying is built into AC, but I see it as a weapon skill and there is no AC difference for someone who is armed vs someone who is not. Also, you could say Dodge is built into AC, but it is an option for action. I suppose you could use the same rule for Dodge as for parry and it's just a matter of how the character wants to imagine their actions. But it takes up a whole action and doesn't allow for any attack. For some characters who have more than one attack per round, it might be worthwhile for them to hold one back for the chance to reduce damage against them.

I missed that part in the DMG about disarming, and now that I look it up I guess I could use that. 

Charging may be not a great idea, but you know there are characters who will try it. Also, it is quite likely monsters would try it against characters. I definitely think there should be a mechanism for this, other than the feat.

I recall threads that included how to handle a non-static AC and how to be creative in combat, both relatively recently. Give them a look, there's interesting stuff there.

If you make "charging" a standard maneuver, I'd suggest making its use circumstantial, and not give any bonuses beyond its ability to chase escapees or closing in distance to engage in melee.

For example:
"When you take the Rush action, if you move at least 30ft in a straight line without going over difficult terrain, you can make one melee weapon attack as a bonus action at the end of your movement."

This makes it a useful tool for the above circumstances, without making it a maneuver you'd use when already in relatively-close combat. Thus you avoid the problem mentioned in previous posts (about how suicidal it is to charge a ready opponent).

I've thought it over and this is how I would work a charge attack - When you take the charge attack option you gain an additional 10 ft of movement (you can't use this attack against a target already within 10ft of you) and lose any Dexterity bonuses to AC  (and have disadvantage on any Dexterity saving throw.) The target immediately gets an opportunity attack against you. Striking with a charge attack causes double damage. A target who has taken the Ready action to prepare for a charge makes the opportunity attack as their reaction but it is at advantage and any damage they inflict is also doubled. 

I don't think that's too complicated. It still makes charging into an attack is a dangerous tactic, but there is some chance for success and characters may want to risk it.

Quote from fromshus >>

It's not harsh - I expected such a response. Thing is, players want to be creative rather than always just saying, "I'll attack," and you want to give them a chance for success, so looking for any other suggestions. 

Quote from InquisitiveCoder >>

Seems to me you're solving the wrong problem. Your players should be picking classes with more interesting combat options (or taking the Martial Adept feat), and the encounters need to be less trivial. Adding more combat actions makes combat more complicated and devalues the existing options that serve a similar purpose. For example, parrying should be something the characters already do automatically because of their AC, and if you want to be really good at it, you take the Defensive Duelist feat.

If you just want to let players have an ad-hoc heroic moment once or twice per session, let them use Inspiration on 1 use of the Charger or Defensive Duelist feats instead of advantage on a roll. Rewarding clever play and enabling storytelling moments is exactly what the Inspiration mechanic is for.

Quote from fromshus>>

My suggestions wouldn't add any combat actions, just the order they occur.

Parrying would take the place of an attack (which would be rolled anyway at some point). And as I mentioned before, dodging is also something characters do automatically based on their AC, yet there is a mechanic for that.

Also, I believe there is a big difference in the play experience between having the DM describe your (automatic) parry to you and you doing something with intention, rolling and succeeding at it. And just as any character can pick up a longsword or don a suit of armour, whether they are proficient or not, I think characters should be able to attempt combat maneuvers regardless of class or added feats.

 

I get what your saying about using Inspiration, but it seems to be a little circular. Do I tell a player without Inspiration that they can't attempt something a little more creative because they haven't done anything creative to get the Inspiration to do something creative?

There is a reason why those maneuvers given to specific subclass and not as general options. I suspect it is to keep things simple and really if someone is not trained it is really hard to do parry, riposte, trip or disarm in a live combat situation and you would get hurt in the process sometimes by your own action even. battle master is the specialized subclass in the feature and if a player wants that kind of playstyle with another class or subclass they can get martial adept feat. What you might be do is (and this is mentioned in DM's guide as alternative rewards) to let a player get trained in martial adept feat as a reward so they don't need to wait or use their ability score increment.

The DMG gives examples of how to run someone attempting to disarm. As for parrying, you can do that by taking the dodge action. Tripping is the shove action.

The battle master is special because he can disarm/shove while also making an attack. Anyone can attempt to knock someone over, the battlemaster just gets to do that ON TOP of his regular attack, and even does bonus damage while doing so.

As you mentioned: any class can make a Shoving Attack to attempt to knock a foe prone (PHB 195). If you want to say that they can use Dexterity (Athletics) to try and trip rather than Strength (Athletics) to shove, the variant rule (Skills with Different Abilities) allows for that (PHB 175). 

Any class can attempt a Disarm to knock an item out of an opponent's hand (DMG 271). Simply put, the attacker makes an attack roll and the defender makes a Strength (Athletics) or Dexterity (Acrobatics) check. If the attacker wins, the item is dropped, otherwise the attack is wasted (if you have multiple attacks, you can attempt this multiple times, or split your attacks and disarms up as you'd like). 

I would add a house rule for both of these attacks stating that using a whip for either action grants the user advantage on the roll, but that's just because I miss my 3.5e bard that used a whip and took feats for disarming and tripping. 

As for the parrying and charging attacks, these are basically already built into the game as well, but in the form of feats, which is basically a more advanced method of fighting. As it is, naturally dodging/parrying an attack is already built into the system by using your Dexterity modifier for AC. The Dodge action is another form of Parrying, which is why a nimble class like the Rogue is able to do it as a bonus action, while other classes have to use an action to do it. The difference between the natural AC dodge granted by your Dexterity modifier and the Dodge action is that you are forgoing all other actions (with the exception of the rogue's Cunning Action) to dodge/block/parry attacks. Furthermore, both the Defensive Duelist and Martial Adept feats give you options for a truer form parrying than your natural Dexterity or the Dodge action. Classes that are more adept at using a more finessed method of fighting (like a swashbuckling pirate) have archetypes such as the College of Swords bard, the Battle Master fighter, and the (aptly named) Swashbuckler rogue that allow for the back and forth dueling that you are equating to parrying. 

Charging is dangerous if not done correctly, which implies that you should be required to be trained in how to attack aggressively. Look at almost any movie where the main protagonist requires training by a guru before they are able to defeat the main antagonist. In these movies there's usually a scene, before their training, where they charge at the antagonist and he utterly destroys them with a few quick movements. Or, the protagonist gets so upset by the guru's methods that they attack their trainer, only to be amazed by their ability to dodge, block, and otherwise avoid all of their attacks, because they are more properly trained. This is the folly with an untrained attacker charging into the fray; they aren't trained in how to charge and are usually dispatched easily by a better trained or more disciplined target. 

Now, mechanically, there are problems with letting anyone do these things without "training" in it.

1. It makes any class archetype that has these features that much worse than any other archetype, simply because you are taking options away from it. For example: why would you be a barbarian if charging gives similar benefits to raging? Why play a rogue when you can just use one of your fighter's 5 attacks per round to parry instead of getting the benefits of Cunning Action -> Dodge?
2. It slows combat down when you give more options to everybody at the table, because:
   • There are more options to think about, which means the player will have to take more time to think about what they are doing
   • There are more rules to have to look up, which will often times have to be read EACH TIME the action is taken, assuming the actions aren't simply a better idea

Now, you might argue with that last part, but think about how much your players have to decide between/look up abilities that are a normal part of their class. Now, add that class ability to EVERYONE'S character sheet. So, you're taking away abilities from specific classes that make that class feel different from everyone at the table AND you're bogging down the game by slowing it up.