Here is the full list of all 19 Rumpus achievements.
Bounce back and forth an object 5 times
Launch an enemy through the top of the screen
In a 4 player match clear all enemies and taunt
Break 200 glasses
Hit 3 players with an explosion
Bounce 500 objects
Grab 500 items
Hit a player with a bounced object
Win a match without moving sideways
Win a match without receiving damage
Win a deathmatch being the only one scoring
Press a useless button in a joystick during a match
Pause a local cooperative match
Break a glass with an object and hit a player on the other side
Play for 24 hours
Beat arcade mode
Beat all arcade time challenges
Beat all arcade levels without losing a life
Unlock all characters