Madballs in... Babo:Invaision

It's a fun 3rd person casual platform-y game available off of Steam and X-Box Live Arcade. Think of something along the lines of Marble Madness meets a simple shooter. You play a spherical rolling soldier armed with a gun, grenades, molotov cocktails, and two character-specific special abilities. In single player mode, there are a lot of tricky platforms to negotiate and huge enemy forces constantly thrown at you. Multiplayer mode is either in the form of a Coop version of the single player campaign or in deathmatch arenas.

The gameplay isn't super deep, but there are definite weaknesses and strengths to different team load-outs. In addition to the 2 special abilities each character has, they also have different movement speeds, health pools, and damage type weaknesses and resistances. There are four damage types in two pairs of opposites: fire/frost (both of which are more AoE-focused: fire burns and frost slows) and physical/energy (both of which are more single-target oriented). The weapons themselves are tremendously fun to use and feel powerful, ranging from fast shooting and potentially destructive physical/energy "butchers" that have a strong pushback and whose fire diverges if held down for a long time to the slow firing fire/frost "lobbers" that act as a ranged artillery weapon that are very powerful from range but can leave players vulnerable in close quarters.

Again, don't expect a game that's going to necessarily require a huge amount of skill or strategy, but a game that'll let you dive in quickly, satisfyingly blow some shit up, and put down after a few minutes for later. The price is right too, only $9.99 off Steam. Keep in mind that balance is still being tuned, and that the PC version will probably get updated more frequently due to the restrictions on XBLA.

So yeah... try it out!