Let's start with a game you have seen a bit of around SCS lately, Borderlands. Both Borderlands and it's sequel are such fun games for people who like to watch numbers go up. Basically it's Diablo meets Halo. It's got a pretty decent shooter system but is far from realism (what with no falling damage, recharging heath and 30 ft jumps). You damage is determined by your gun and crits are determined by hitting vital area, i.e head shot for humanoids. You have a second wind system where if you are killed you have a short time in which you can get a kill and stand right back up with some health. The whole game is very hectic with a strange but funny sense of humor...and a very annoying dancing robot. It can be casual or addicting but it's a fun game solo but waaaaayyy better with 3 friends.
Next is another game we streamed, Multiwinia. It's an RTS...kinda...but with like human nature elements...and uh. OK look I cant really explain it so if you want a crazy RTS like you have never played you and your friends should grab a copy and look months of your life taking screen shots of the epic battles you have.
Finally I dont believe we have streamed this one yet but we might some day. Dungeon Defenders is the Borderlands of wave defense. You have a class, you constantly get barraged with weapons to compare to your own, and you can't stop playing till you have the highest numbers...with no real end game. This game starts very easy but the difficulty ramps really high but its worth it. Each class is unique in its play and there are far too many combinations of weapons and gear. This game isn't for everyone but if it hits sale again for the 5 bucks i bought it for it will definitely be worth a try.
Alright guys sorry for the day late and I hope you enjoyed my recommendations. As always leave your own opinions in the comments and share this shit with your friends.