I managed to get myself stuck in the first gate as I attempted to run through, and wasn't able to escape its vice grip.

Genocide%:  Kill any and all NPCs in every level, yes, even the Nullrats.  Infinitely spawning enemies (such as the hordes in Time Tower and Throneroom) are exempt.

Sourceruns%:  Complete the game by bunnyhopping backwards.

Buttonmasher%:  Press all the buttons in the Museum as fast as possible.

One in the Chamber%:  In order to use a gun, you must chamber a round and eject the magazine immediately after.

EmptyMag%:  Softlock yourself in the Breakroom as fast as possible