Except you erijfecoetmpermterfoekrof (Stupid questions need stupid answers)
The ability to save 50 people and only 50 people once an apocalypse happens

You save 50 random people but the 50 people you care most about die

Ability to retrieve any memory and write it down before I forget it

Inability to ever find anything to write with.

Ability to bend reality to fit your every whim.

It takes a lot of strength to bend the whole reality; when your muscles become tired and you release your grip on reality, it bends in the opposite direction.

The ability to post a superpower that hasn't been posted yet

You automatically get all side effects, whether that have or haven’t been posted

The ability to instantly change what type of pen I am using

You write in invisible ink
The ability to manipulate gravity to your heart's content

That gravity manipulation affects you, meaning you could be crushed or boil according to how you change it.

The ability to stop time, but be able to move freely when time is stopped.

You can’t unpause it, but you still age and have needs normally.

Ability to change into whoever you want

The other person becomes you and you can’t change back

The ability to merge 2 animals into a new one

The 2 halfs of the animals that didn't get merged, will merge to an evil version of whatever you created, and it will try to kill you

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the ability to finish my report that was supposed to be done 2 weeks ago instead of browsing OT forum....

You will only be able to finish any report exactly 2 weeks after it was due.

The ability to remember everything I have ever learned and everything I learn in the future.

Except you can do only that, and nothing else.
Becoming the Ultimate Survivor (i.e. being like Rantaro Amami from Danganronpa)

You can’t survive more than a day

Ability to yeet

...only the length of your arm

The ability to make good music and people appreciate it

However only when they listen to it alone, they're always too embarrassed to share it with friends as something they actually would listen to

The ability to breathe fire

Your mouth gets scorched
The ability to make water flow against gravity

you are allergic to water

ability to instantly optimize the strategy to any video game

... any video game from the 1980s

The ability to erase really good

you make a mistake roughly every letter/number, meaning you have plenty of time to practice that power

a photographic memory