These are ways to speedrun some categories.

If you strafe using A + W or D + W you can walk faster. If you want an extra knife at the end for Killeveryone%, you can throw all your knives at the end stair and when the fade-out starts you pick them up, the game will give you an extra knife since you finished a level without any. You can change the strafe from one side to the other making easier to go through doors and to get some time saves.