The speed boosters in this game usually function more like obstacles than bonuses. More often than not, they send you careening into a corner at 500 KM/h.
A couple suggestions, from a relatively new player.
1. A Bestiary:
I like the idea of having a log of all the creatures you've encountered and defeated through the game. Maybe it'd list the monsters' stats, instead of just their HP and MP. (If they have stats.) Maybe it'd list a little trivia tidbit relevant to the monster, or a joke, or a suggested strategy for defeating it.
2. Some sort of "Morphing Ability:"
What I'm imagining is something that allows you to change your sprite (not your stats, or anything like that) into that of a creature. For example, my character could look like a Skele, or an Ogre, or etc.
This might not work with things like spiders and crabs, so maybe only humanoid creatures would work.
As for implementation, maybe after you kill 1000 or whatever number of creatures of a certain type, you gain knowledge of their "essence,", and when combined with the right "magical crafting" routine, it changes your sprite.
Nothing like playing a decently tough game with the added "lag difficulty."
Oh, I'm sorry, did you want to wall jump there? Haha, I thought you'd rather like to fall to your death.
 "AdVenture Capitalist"){kind=icon}
 "Monster Arena"){kind=icon}
 "Jet Velocity 3D"){kind=icon}
 "Fantasy Online"){kind=icon}
 "Kommunicate Rev7 (Alpha)"){kind=icon}
 "Meat Boy"){kind=icon}
Yeah, and it works now, finally.