Useless useful powers

As the title implies, I want to make Heart an awesome power. Give an example of a power that sounds useless or crappy on paper but has potentially lethal applications.

I'll start with one, a character has the ability to talk to animals, not control them or read their minds, just talk. With this power they still can ask animals to help them.

Oh, I got plenty of these...

(All quirks for a MHA-fan fic in my mind and in its development stage)

"Mighty Marshmallow"

The touch-based ability of granting stuff the properties of marshmallows.

Sounds dumb?

Most obvious use, make your own marshmallows (one property is that they're edible after all), whenever you get a sweet tooth-urge. Take a leaf and...well.

Now, how to use it properly

Offense: Break anything by turning the stuff you want to tear apart into squishy soft marshmallows. Turn living tissue into marshmallows, effectively rendering the opponent powerless by turning their muscles as soft as marshmallow but nothing else. Melt walls and rubble away by turning it into marshmallows and bring a flame to them. Turn people immobile by turning their bones into marshmallow and watch them harmlessly collapse down.

Defensively: Turn your impacted areas in a fight temporarily into marshmallow to soften the blows. Marshmallow-tissue doesn't bleed, so if shot or stabbed, turn the wound into marshmallow, get the bullet out, close it, and turn it back to normal. Survive high falls by full body conversion into marshmallow to dampen the blow.

There are more functions to this power, but I got no time to put the whole list out now.

Not "useless", per se, but one that might not seem dangerous at a glance:

The ability to purify any water you come into contact with. At a glance, it seems like the perfect superpower for a pacifist, like something that couldn't possibly used for evil.

Here's the thing: we're mostly water. Such a character could theoretically kill people by opening a small wound and turning this person's entire bloodstream into water.

The ability to change the color of objects, for the most part it would be useful for art projects, but in the right hands it could be used for camouflage, disguising poisons or potentially blinding people by changing their pupils

If you're feeling sadistic, you could wound someone and then change the color of their blood and skin to make it look like they got a nasty infection or disease to make them misdiagnosed and possibly killed by a doctor later

A good way to think about it is not trying to apply every single seemingly useless power to fighting and combat. Like others have said a lot of powers can be useful, and would even make you rich in the real world but have no combat applications, really.

Here's another one:

"Fish and Bread: Rush Hour"

The power to multiply anything that fits into the user's hands by a thousand. (limiting the size of objects that can be multiplied) and the copies decays like organics, regardless of what they are, from the moment they're made, to ultimately vanish completely after one hour.

Can it be used to multiply by less, say, 10, if needed? Or is it always 1000?

It's a set value, aka "always a 1000"

Hence the "useless" label-half on the power.

Aaaah ok. I thought the useless part was covered (also) by whatever they create disintegrating within an hour even if they would need it for longer.

That's actually what makes the power tolerable (as far as the user is concerned) since it's one thing to make a thousand of something in a hurry, it's a whole other to deal with the consequences of having it still around once it's no longer needed.

Ability to hide information about oneself.

It's actually a very useful power because it basically gives unparalleled stealth, immunity to Combat Clairvoyance (can't see the future if you don't get info about the target), immunity to Power Copying and shapeshifters (since the copier doesn't get any information), immunity to opponent's Adaptive Ability (adaptation requires info about the target, and if that's denied...).

If taken further, it can get downright overpowered because if one's mark on reality/presence in existence counts as a form of info, it also means the enemy can't do a thing to them because the user technically can make themselves nonexistent to others.