Ok anyways... today I have a more sensitive topic... yes FOSS gamers have lives too. Hard to believe I know, but out there (yes, outside of your parents basement... the place where yo go for geo-caching) people have real parties (without the LAN- suffix) and they use FOSS games during those occasions! At least some do ;)
Some of these strange species can be seen in the following promotional video for Performous (beware SFW underage nerd chick action):
Performous is a all-in-one party game, meaning you will have the choice to embarrass yourself in front of your best friends (or clueless cannon fodder as we FPS hardcore gamers say ;) ) either by singing, dancing, drumming or strumming (e.g. guitar playing) (embarrassment level in the same order). But of course... Karaoke is only fun super drunk anyways... so you just have to fear the You-tube videos of your performance the next day ;)
Speaking of Karaoke: There are two other FOSS applications for that. Canta and Ultrastar Deluxe neither of which I have tried, but they probably do the job fine. And for dancing (well if you can call it this way... call me old fashioned but for me dancing normally includes a woman, preferably very close ;) ) there is the granddaddy of all FOSS party-games: Stepmania. But yeah, you will need to have one of those dancing mat controllers you can pick up cheaply on Ebay.
My personal favorite however is FoFix, a fork of the pretty well known crazy keyboard destroying FretsOnFire.
FoFix adds most notably multi-player and full band support to the guitar only experience of FoF. Oh and yes...it does support more pretty (albeit non-FOSS) themes from its commercial counterparts if you fear your non FOSS-gamer friends will be shocked by common programmer's art ;)