Geometry block: a 4x cube that can kill you if you touch any side but the top
Geometry spike: just a 4x triangle
Geometry player: Just a block model dust is behind the player when he moves, jumps far but only just a bit higher than a 4x cube , really fast, standing still for too long will kill it
Rocket (Vehicle) holding space makes it go up, but slowly goes down if not, dies if still for too long the model is just a longer version of the spike
UFO (vehicle):think flappy bird, pressing space makes it go up but it falls down fast the model is just a 6x6 plate sorta thing
Razor, right click to make the player fly up to the ceiling right click again to go back down
Geometry dash music: those tracks are good!
Jump boost: when nearby the player can double jump
Trampoline: just the brick, players can make the brick bounce the player themselves
if you want to actually make the models instead of using the simple ideas I talked about that's fine