Take that, Physics!
Very rare3.6%ObjectiveOptionalAnywhere
Jump on five big bullets in one round
You actually have to jump on 5 fat-gun bullets without touching the ground. Each one you jump on give you another double-jump. An easy level like Foyer 1 makes this easier to get, or a Deathmatch with custom rules and a 2nd player to just repeatedly fire shots with the fat gun for you to jump on.