In this thread, I'll post things that I think are fun or funny to do in D&D. Feel free to join in, but don't worry about tactical implications and don't argue!

1) At 6th level, Tempest Clerics have the ability Thunderbolt Strike. Assuming you got to pick up a cantrip from another class somewhere along the way, you can use Lightning Lure to pull an enemy 10 feet closer to you, deal 1d8 lightning damage, and then immediately yeet them back.

If your DM is cool with it, a monk can take two levels of Paladin and equip a Light Hammer reflavoured as knuckle dusters, or gaintlets... or something... and then you can Falcon Punch, because everyobe wants to play Captain Falcon.

Use minor illusion or prestidigitation to mess with people. Especially dropping sounds to misdirect them away from where you're sneaking. It's not so much the mechanics of it but the creativity of choosing the effect and trying to get the party and the DM to crack up. 

A level 20 Redemption Paladin slowly killing enemies with nonviolence via Emissary of Redemption, and you can use Aura of the Guardian to deal a little more damage by circumventing your resistance to all damage. You can also add Shield of Missile Attraction on top to protect your allies and to soften up some of the ranged enemies without needing to use a reaction.

Homer Simpson - "Oh, yeah, what are you gonna do? Release the dogs? Or the bees? Or the dogs with bees in their mouth and when they bark, they shoot bees at you?"

Moon Druid + Swarmkeeper Ranger

As a 15th-level conjuration wizard with conjure minor elementals, you can summon 24 steam mephits with 30 extra hit points (using an 8th level spell slot), and win by pure action economy.

Yeah as a DM I'd forfeit the combat before sitting through a combat where the PCs have 20+ turns per round

The fact that the very rare magic item Marvelous Pigments, with which you can paint anything and it will become real as long as it is not anything worth more than 25 gp, can technically print money since you can still make a platinum piece (which is only 10 gp) over and over and over to the point where you can just buy more marvelous pigment and continue printing money. I did this in a game once, and ended up with over 500,000 gp. Please note that this game was very silly and I am pretty sure no smart DM would ever let their players do that. 

According to Storm King's Thunder, a pc can wield a Fire Giant's Dagger as a greatsword that does 3d4 piercing damage.

Quote from _Mordecai_ >>

The fact that the very rare magic item Marvelous Pigments, with which you can paint anything and it will become real as long as it is not anything worth more than 25 gp, can technically print money since you can still make a platinum piece (which is only 10 gp) over and over and over to the point where you can just buy more marvelous pigment and continue printing money. I did this in a game once, and ended up with over 500,000 gp. Please note that this game was very silly and I am pretty sure no smart DM would ever let their players do that. 

 Once when I was stuck in a Forcecage I painted a door on the wall and let myself out. :)

While the Band of Loyalty is mostly used for lore purposes to make it impossible to interrogate spies, it's so much funnier if you think about it in the context of a married couple.

A female warlock/beastmaster ranger with a lion beast companion in an enclosed wooden closet would be called a Lion and a Witch in a Wardrobe.

Forget waiting for polymorph to sneak your stuff into the royal banquet: Have your Genie warlock enter their urn while carrying your weapons, and you can even pretend that the urn is a gift for the royal hosts -- in more ways than one.

At 7th Level, an Oath of the Open Seas paladin with the Grappler feat can pin other creatures without becoming restrained. 

When dealing with Lycanthropes, silver coins can arguably used as an improvised thrown weapon to bypass their immunity to non-silvered attacks 

I enjoy watching a party get creative after they realize they can make 2 gallons of mayonnaise with their alchemy jug.

Quote from Kaboom979 >>

At 7th Level, an Oath of the Open Seas paladin with the Grappler feat can pin other creatures without becoming restrained. 

 Pretty sure the paladin in some DND webcomic took a pouch and some silver coins to combat a pack of werewolves, pretty creative lol. 

Levitate + Gust

A poor man's Fly.

Chaos Bolt has the potential to deal 2d8 + 1d6 damage to infinite creatures.