Reflavouring spells to fit specific characters is one of the most fun things to do. It can be an exercise in character creation and show off the nature of your character! Tell me your favourites that you've thought of or seen played! Haven't really seen a thread about this anywhere.

Some of my reflavours:

(Oath of Vengeance, dual wielding two long swords.)

Smite: The flametounge sword's flame changes from a classing orange into a combination white, pink and pale green and leaves a light trail behind

Shield of Faith: 5 spectral swords float the creature defending them

ps. If anyone has any ideas for a paladin casting haste, please do tell! I'm stumped for ideas.

I can see a Paladin's haste manifesting as small spectral wings that appear on their feet, similar to Hermes as a reference to a source of divine speed.

My College of Spirits Bard's Mage Hand is a ghost reaching through the veil. Mostly, though, I keep close to the default descriptions.

I haven't started a campaign with him yet, but I have a Tiefling Artificer who I'm planning to do a lot of spell flavoring, since that's kind of the bread and butter of Artificers moreso than most other classes.

He's a Mammon Heritage Tiefling, and I'm planning to flavor the spells he gets from that differently from his Artificer spells. The Subrace gives the Mage Hand cantrip instead of the usual thaumaturgy, so I'm planning to have it as a golden, monstrous looking hand that has a bit of a mind of its own and tries to steal stuff. For Tenser's Floating Disk I'm planning for it to resemble a giant cold coin, and the last spell the subrace grants is Arcane Lock, which isn't so flashy but basically any lock he touches briefly turns gold.

Other than that, the hardest thing about trying to reflavor Artificer spells is explaining how Concentration works. I'm planning for him to essentially have a "Power Glove" with switches and knobs all over it that he needs to constantly fiddle with and adjust while concentrating on spells, otherwise the energy overloads and breaks the spell. Losing Concentration then is less about having his focus ruined so much as it's just getting too overwhelmed to maintain the delicate technology he relies on.

This ain’t a spell, but my Artificer Artillerist in a fantasy campaign uses “Improvised Wands” in place of Eldritch Cannons.

Most of the spell effects from my Cleric/Paladin are of a more creepy sort because he leveled up in Curse of Strahd so his magic was touched by the Shadowfell.

On the flip side, I once saw someone playing an Arcane Trickster Rogue who flipped around using Acrobatics and most of her spells looked like glitter.

Usually when I cast Mage Armor, instead of a magical force-field, I like to think of it more as the magic amping up my reaction time instead, allowing my character to dodge incoming blows. Once when I was playing a Divination wizard I even said Mage Armor allowed him to look split seconds into the future to avoid danger, like a spider sense. 

I did bunch of reflavoring with my most recent character: A changeling warlock of the Genie(Marid - but ice flavored). He's a Bookworm and loves stories , all his Spells and abilities are either some sort of icy script/icy blue light or have some kind of book or paper involved. When he uses Misty Step a big book shuts around him and he apears out of his tome in another place. His E-Blast is icy blue and has swirling letters behind it, his Hex is basically a belt of writing spelling things like "You have been cursed".

I’m playing a Pact of the Genie Warlock in a new campaign and his patron is an Efreeti so his Eldritch Blast looks like a blast of Fire. Not quite a Fire Bolt, but similar. 

I flavor most of my spells on the fly because it’s more fun. It doesn’t change the mechanics, just the role playing. 

I'm playing a wizard that among other things, heals! Through necromancy! My re-flavored version of cure wounds, for example, is called mend flesh. You can feel the foreign animating force enter your body for a second and your flesh moving inside your body to stitch itself back together, lightly restoring wounds. In exchange for a smaller dice size, it can work on undead as well. Or anything made of flesh, really. I am a school of necromancy wizard, but zombies and such are just the result of failed resurrection attempts in a world where reviving the dead is a difficult and rare (if not impossible) thing, so my character is not a huge fan.

I ended up making more healing-focused reflavors borrowing from other classes' spell lists, (accidentally made a low-level version of a lich's tether ability intended to only help my party members by reducing/taking damage for them, before realizing there's an official spell for it!) but had to change up some other spells to fill needs in ability and backstory as well. Over 13 spells at this point, because I got way too into it. Three very important characters from my backstory were spell casters of various classes as well, so I'm also planning on just renaming some spells after them if they fit their personality or abilities.

Generally I try to avoid changing mechanics too much, and if I do, I find multiple spells of the same level to base them on.

I know I'm gonna have more homebrew spells than it's feasible to learn in game but it's too fun.

I am playing an air genasi mountain ranger/ storm sorceror with witch bolt that she calls storm bolt.

I have a Locathah Swarm Ranger/Genie Warlock with a jellyfish theme. The Pact of the Chain familiar is the "boss" jellyfish and the various swarmkeeper features are all smaller ones. Faerie Fire is the swarm going bioluminescent in an area, and Hold Person is the swarm working together to paralyze the target with neurotoxins.

Of course, my genie's vessel is a fishbowl.

Is the usual practice to rename the spell, &/or change the descriptive imagery or what happens when you cast a spell and what it looks like/sounds like/feels like, etc when you cast the spell, but leave the mechanics of the spell  unchanged?

Do you try to have a cohesive THEME with some or all your spells and they way they are flavored, that plays into or enhances  your character's subclass/subrace/personality/quirks/traits etc?

After you've put in all the work and worked with your DM on flavoring spells,  do you do the thing that you came up with every time you cast that spell and then, if so,  is that going to be rewarded in fun for everyone at the table, or is whatever  the awesome spell flavor is, is that  going to get old after a while too? (or does it become like a beloved familiar  thing you always do , or  maybe like.a running gag?)

Quote from intrepidgnome >>

Is the usual practice to rename the spell, &/or change the descriptive imagery or what happens when you cast a spell and what it looks like/sounds like/feels like, etc when you cast the spell, but leave the mechanics of the spell  unchanged?

 Not to rename it, usually, but yeah, the rest of it for sure.

Quote from intrepidgnome>>

Do you try to have a cohesive THEME with some or all your spells and they way they are flavored, that plays into or enhances  your character's subclass/subrace/personality/quirks/traits etc?

Basically. I think most people don't do it for their whole spell list. You try to get a spell list that mostly works on its own, and then adjust the ones that don't fit.

Quote from intrepidgnome >>

 is that going to be rewarded in fun for everyone at the table, or is whatever  the awesome spell flavor is, is that  going to get old after a while too?

 A very good question. I've often felt it drag, myself, but I'm also kind of a slow player so I often feel the pressure to get my turn over with, sans extraneous description.

I played with a fella in a AL group whose gloomstalker ranger spells were different mushrooms that he ate to cast. Literal magic mushrooms. 

Quote from intrepidgnome >>

Is the usual practice to rename the spell, &/or change the descriptive imagery or what happens when you cast a spell and what it looks like/sounds like/feels like, etc when you cast the spell, but leave the mechanics of the spell  unchanged?

 I think it only appropriate to rename the spell if the element damage changes - fire instead of poison damage. Otherwise, mechanically it doesn't matter what the special effect of the spell is as long as the numbers stay the same. I let my players flavor their spells however they want as sit makes them more attached to their character. You want rainbow butterflies for magic missiles? no problem.

I think "reflavoring" ends with changing of the damage type for most people, since it can have a mechanical benefit (I'm not against it, but I'd call it homebrew and I'd probably allow it). I think anything that is just visual, sound, smell etc. are all free game, I wouldn't care if someone changed the name of a spell (especially in cases like mordenkainens magnificient mansion and the other named spells)

I reflavor/custom flavor spells all the time.

I have a Lore Bard/Sorcerer, whenever she casts chill touch she plays a dirge on her lute and the music forms the skeletal hand as it travels through the air, whenever she casts mind sliver she plays a discordant note, and whenever she casts mage hand she whistles like Yondu to his arrow.

Whenever my Artificer casts thorn whip it’s a spool of barbed wire that launches out of his infused crossbow.

One of the players in the campaign I was DMing was playing a Fighter/Warlock with the Fathomless patron who reflavored his mage hand as a mini tentacle.

I have an Artificer that just LOVES electricity. Most of his spells are reflavored forms of getting shocked.