My evil transmutation wizard likes to pickup monster bits to make new abominations.  Ritual Casting Gentle Repose keeps his bags from smelling like a slaughter house since the DM won’t let him have a bag of Colding. 

Quote from Beardsinger >>

An uncommon use for a commonly used spell.

If you have a rogue / scout type that often goes off ahead of the group you can drop hunters mark on them in case of emergencies…. “you have advantage on any Wisdom (Perception) or Wisdom (Survival) check you make to find it”

I don’t remember the specifics, just the general reaction from the rogue player when he said he wanted to go scout for traps. Another player said “don’t split the party”, and I came back with “I cast hunters mark”.

I mean, if you really want to make sure you know where the rogue ends up on their little jaunts, you can always mind spike them and ask them to fail the save...

Whenever there is any number of flying creatures my party loves to dump whatever spell slot they may need into sleep to get as many of them to fall to their death as possible.

I remember when we were fighting a specter that had gone mad because a crystal that was sacred to it broke in half. The party cleric surprised the DM by mending it.

Quote from BoringBard >>

I remember when we were fighting a specter that had gone mad because a crystal that was sacred to it broke in half. The party cleric surprised the DM by mending it.

You managed to stall the specter for a full 10 rounds?

Quote from quindraco >>

Quote from BoringBard >>

I remember when we were fighting a specter that had gone mad because a crystal that was sacred to it broke in half. The party cleric surprised the DM by mending it.

 

You managed to stall the specter for a full 10 rounds?

 We got some decent persuasion rolls and also it was a: "You'll probably fight this but have time to try and communicate" type of combat thing.

Edit: 1 minute seems a lot longer in combat than outside of it. When playing the game, minutes (in and out of game ones) fly by easily.

I find it hard to think of specific examples, as I pick loads of spells that online guides tell you to ignore, and I suspect a lot of players probably do the same, so it's hard to know what exactly underused might mean; does D&D Beyond have stats on the number of characters a spell is chosen by compared to the total for each spell level (as obviously 9th-levels are a lot less common than 1st-levels)?

For example, I've seen guides saying not to bother with unseen servant but on my Strixhaven Wizard I've never not used it in some capacity during a session; you can cast it as a ritual from a spellbook (thus far I've learned exactly 50% of my spells as rituals, so my wizard can cast every spell he knows without long resting). When he's feeling lazy he has the unseen servant grab him under the arms and drag him around, I've used it to pants a guy I didn't like, I've used it to pick up objects in rooms where I was worried they might be trapped. Between the unseen servant and his familiar (Ferret, the weasel), Edward Merryspell has almost never touched anything first in this campaign, and it's kept him safe from so much potential harm.

I've seen a few saying not to bother with light when you can just have a torch, but you need to hold a torch meanwhile you can cast light on the tip of a spear so you're both armed and able to see; I used this a tonne on my Aarakocra Cleric/Monk in a Frostmaiden campaign.

I'm also a huge fan of cantrips such as druidcraft, prestidigitation, shape water and thaumaturgy, because I find it tremendously fun to come up with creative uses for them. I do still feel that druidcraft should come as standard on Druids (it's a tough sell as one pick out of two), but there are so many feats now that allow for more cantrips that this is less of a problem. I love, love, love these cantrips on characters and I get so much enjoyment out of them personally. I take prestidigitation on everything that can, and use it at almost literally every opportunity; my Bard has both it and thaumaturgy, so he never opens a door by hand, or light a candle, he's always reflavouring people's food and drink, cleans himself (and only himself) after wading through mud or whatever and so-on. But again these aren't cantrips you'll see on combat-focused build recommendations, it's usually about squeezing in at least one attack cantrip, one or two save based ones, a good range of damage types etc., but I rarely build my characters with more than two damage cantrips.

On that note, I'm actually also a fan of acid splash; maybe I just have more generous DMs but while it's not amazing against single targets (unless the DM allows it to hit larger targets twice), against multiples it's fine, plus you can always suggest using it to melt things.

I've also used blade ward on a sorcerer as a shield against traps (it's a cantrip so just cast it every six seconds), the main issue is that it only specifically works against "weapons" so you need to have a conversation with the DM about whether traps will count or not. I've also used true strike, though I agree it's not a great pick on most builds, but it can be useful for a Sorcerer since you can quicken it for a later round when you're going to cast a big attack spell. Tasha's did give us Seeking Spell, but Sorcerers get cantrips faster than metamagic choices, and there are so many ways now to pick up more, plus it stacks so if you have a lot of attack spells you could take both to make it very hard to miss.

Across multiple campaigns I have close to a 100% success rate at enemies failing their saving throw to grease.

This includes the bosses at the end of Storm Kings Thunder.

If it is an available spell choice for the class I am playing, I always pick it.

Heard of a character in a friend's campaign who will use Move Earth to create a 5' divot with a 5' mound in "front" that the Ranger uses for cover while shooting his bow.  Not perfect enough to be game breaking, but a creative use for it, I thought.

Quote from Falwith >>

Heard of a character in a friend's campaign who will use Move Earth to create a 5' divot with a 5' mound in "front" that the Ranger uses for cover while shooting his bow.  Not perfect enough to be game breaking, but a creative use for it, I thought.

Yeah, move earth is fun for creating environmental advantages. I had a wizard trapped in a classic 'spiked ceiling descending in a room' trap with a dirt floor, and he used move earth to make a trench for himself to lay in

I like using Mage Hand for sabotage purposes.  It's amazing what you can do with a little straw and a lit lantern.  It's extra effective with the Telekinetic feat letting you make it invisible.

Oh! Speaking of Mage Hand, I finally have one to contribute!

I love using Mage Hand to trip traps. For example, we came across a series of manufactured tunnels. I used my Mage Hand to slap against the walls and floor, and BEHOLD! The tunnel collapsed. I went to one of the other tunnels, did the same. Tunnel collapsed. Went to the next one... tunnel didn't collapse. That's the way we go.

Quote from Torvax >>

I wouldn't call this an underused spell, but maybe an underused feature of one. Tongues can be via touch targeting other creatures, allowing for them to understand any spoken language, and more interestingly is that anyone can understand what it says provided they can speak at least one language. Sort of a way to give voice to the voiceless, such as creatures created via spells like Find Familiar/Steed, Create Undead, and Animate Objects if you really want some options to freak out your local npcs. 

 
Only works on targets that can speak. Familiars, the undead made by create undead and the animated objects, etc, cannot speak. 

It doesn't grant the ability to speak. 

Quote from Torvax >>

Quote from Cyb3rM1nd >>

Quote from Torvax >>

I wouldn't call this an underused spell, but maybe an underused feature of one. Tongues can be via touch targeting other creatures, allowing for them to understand any spoken language, and more interestingly is that anyone can understand what it says provided they can speak at least one language. Sort of a way to give voice to the voiceless, such as creatures created via spells like Find Familiar/Steed, Create Undead, and Animate Objects if you really want some options to freak out your local npcs. 

 
Only works on targets that can speak. Familiars, the undead made by create undead and the animated objects, etc, cannot speak. 

It doesn't grant the ability to speak. 

 

Animals speak just fine to each other, be it by body language, odor, or very literal speech with vocal calls. Zombies can have access to somewhat intact vocal cords, skeletons may need some rudimentary sign language. Animate Objects is a bit of a stretch I'll admit, but tap twice for yes system could be something employed. The real question is if any of these creatures would even have anything to say, and I would leave that up to the DM.

 Unless the creature's statblock lists at least one language that they can speak, Tongues will not affect them.  "Body language" is not a language as recognized in the game.

In our new campaign, I am running a kobold draconic sorcerer, and I am getting a lot of mileage through Tier 1 with create bonfire. I have managed to use it as a distraction, some battlefield control, and a little damage. Our DM even commented on its varied uses. We just hit level 4 so I doubt it will continue to have the same usefulness going forward. 

I like using minor illusion for hiding. It can make an illusion large enough that most characters barely need to squat to hide within it.