The title character of Magical Mina, part of the Tsunami Channel ...uh, franchise? ...does this sometimes, with this being a particularly good example. She's also adapted her Sword magic for a scalpel. Of course, she was written to be an exceedingly clever and intelligent Magical Girl. Also, here.
She also has a device that can rewrite DNA, which she uses to rewrite her own DNA; not for self-mutation purposes, but because her flash drive doesn't work and she needs storage space. As if that wasn't crazy enough, someone else wrote a message into the DNA of all life on Earth, containing a spam letter advertising a pyramid scheme.
Ron: Do you keep a tally of all your affronts to nature?
Parodied when Xykon orders Redcloak to use Speak With Dead on a fallen Mook, thus tearing said Mook's soul from his eternal resting place so Xykon can ask him...where Xykon left his keys (in his own pocket). Which is odd, as the spell uses knowledge imprinted on the body... but theory neverwas Xykon's strongest side.
Xykon: Thanks! The conjuring of his immortal soul saved me the inconvenience of digging out the spare set I keep in my desk.
When Belkar decides to multiclass as a Barbarian, part of the guild-leader's pitch is that the enhanced speed the class grants is excellent for getting to the front of a buffet line.
When Belkar acquires a Ring of Jumping, he mentions that it will be good for both raining death on his enemies, and getting items down from the top shelf.
There is a waitress who is training to be a ninja. This allows her to appear at the table out of nowhere, or dodge objects thrown by nearby irate customers in a pinch.
When Belkar acquires the skull of an Eye of Fear and Flame, he comes up with a number of uses for it. The skull draws the line at 'chamber pot.'
Belkar uses the firebreath of a demon cockroach to cook a pot of stew.
Look sharp, or you'll miss seeing a cauldron of fires from the ghastly inferno that is the Lower Planes being used for...making popcorn.
Tarquin accuses bards of suffering from this trope. He thinks they could use their knowledge of narrative structure to rule the entire cosmos, but most of them are content to use it to entertain tavern patrons instead.
Used in thisExterminatus Now strip. The next strip actually deconstructs this trope a bit; their mundane overuse of Rogue's beam sword has drained it of its power.
The reason the computer of the Savage Chicken wants to kill Sam is because he and Helix used high explosives to make popcorn, thus damaging some vital components of the ship with hypervelocity popcorn kernels.
Bob the Angry Flower loves this, from creating a monster to fix his printer to bringing Jesus through time for girl advice.
In the world of Nature of Nature's Art, odd as it might sound, very few of the setting's superpowered martial arts styles are exclusively used for combat. In fact, some aren't supposed to be used in battle at all...which doesn't stop certain characters from doing so.
Kid Radd and his gang met up with a world of NPCs who are all invulnerable and don't feel pain. They use their power for fun party games like 'Pin the Tail on Anything That Moves', 'Five Player Badminton (They use each other as the ball and rackets)', 'Musical Bear-Traps', and 'Blatant Pyromania (Just setting themselves on fire)'.
In Sequential Art the Denizens used the ray gun technology they stole in personal weapons, Kill Sat and a popcorn popper (and it's a plot point too).
In Two Evil Scientists, Wily and Eggman use their powerful shapeshifting robots to disguise themselves as Amy and Roll and babysit for Wily's daughter Cream, while the real Amy and Roll are imprisoned by the two scientists. This bites them in the ass later on when the robots betray them partly because of being used mundanely.
Driders and other spider hybrids have a handy supply of homegrown silk for tailoring. One of the best tailors in Drow Tales is a drider, and Spinnerette decides to try her newfound powers out by knitting a silk scarf, and later makes her costume out of her silk.
Also from Spinnerette, Sahira uses her newfound powers out in this strip to clean the flat in record time.
The Last Days of FOXHOUND: virtually every team member who has special powers has used them for petty or useless purposes at least once. Decoy Octopus uses his near-infallible disguise powers to play practical jokes and blame Liquid; Revolver Ocelot, having gained an immunity to mind-reading, uses this to mess with Psycho Mantis; and both Mantis and Bernard have used their psychic powers to annoy people or obtain free stuff.
Homestuck: Dave Strider uses his Knight of Time timey-wimey superpowers to a) play the stock market, and b) move from a cold place to a warm place, then go back in time an hour in order to continue a Pesterchum conversation.
It still doesn't stop some people, though. Examples include: Cinna using her Playing with Fire ability to prank Gravity Master Muneca, who sometimes respond in kind; Making a Splash Larima loves to show off; and Blow You Away Enlil prefers to fly when a more ground-bound transportation would've gotten the job done.
However, there is a "petty" purpose which is a big deal to Taffe (Larima's sister): she is deaf, and she uses her Make Me Wanna Shout power to amplify sounds so she could hear.
The main reason for Seren's Power Limiter is so she can put her own powers to mundane use—without it, her "Spell Booster" nature drastically amplifies any attempt at magic.
During her tenure as director of the International Mages' Alliance, Seren wrote a slew of joke magic books just for fun, like "Magic to Make Cats Be Friendly" and "The Encyclopedia of Magic to Make People Laugh". However, Meguru found them to be full of informative explanations of magical theory.
Tamaryu attempts to use her fire breath to cook but ends up setting the kitchen on fire.
Many magical or high-tech characters use their powers for mundane tasks in Roommates from abusing teleportation because to lazy to open the door, to decorating, or dressing up, or cook etc. This went so far that the magicless part of the main cast imposed rules on the Monster Roommate because of it. (He isn't allowed to teleport in (because it causes clouds of glitter which is a pain to remove) and change their clothing unannounced.)
Metacarpolis: Emi, a former magical girl turned cleaning service maid, transforms her magical rod into whatever cleaning tool she happens to need at the moment.
The Whiteboard: Doc invented a teleporter, he gave it to the pizza place for instant deliveries.
MegaTokyo: Magical Girl superspeed can be used for fighting monsters, stealing weapons away from enemies, Roof Hopping...or cleaning. Not to mention holding a text message conversation in the middle of a fight. On a more subtle note, one girl finds it easier to keep up with her hyperactive Genki Girl friend once she gets her powers.
Xaneth's Crystal Ball in True Villains is the transformed eye of a God, an artifact of tremendous power that lets him scry across the continent, granting him an unmatched tactical advantage... and saving his team the two-second hassle of casting Telepathy spells to contact each other at a distance.
Harem of Grrl Power can duplicate herself, creating up to five bodies linked by a single consciousness. Similar to Jamie Madrox of various X-Men spin-offs, she'll use her multiple bodies to learn multiple skills simultaneously. She'll also take the opportunity to enjoy multiple items from a restaurant's menu, though she has to be careful about flavor combinations if two bodies eat at the same time.