After years of diehard BSD use,* I've plunked a Ubuntu machine on my desk so I can be lazy and enjoy some often-working desktop magic "out of the box."
So, now that I'm one click away from a good chance of a pretty-much-working install of anything out there, what's "fun?" I'm asking here because I know y'all have pretty good taste!
To limit things somewhat, try to leave out the following:
* Emulators: That's cheating, and UAE would win anyway, right?
However, particularly awesome
new games that happen to target an emulator are fair play.
* Roguelikes / UNIX classics: Personally, I have a hard time getting into these; for purposes of argument, let's assume everyone's already heard of them?
* TuxRacer, TuxCart, Frozen Bubble: The three "decent-quality" projects everyone's heard of.
* Quake: I know, I know, I know! But if something completely different just happens to make use of the engine, let me know.
I won't put them on the list, but I've already enjoyed TetriNet and xgalaga for years, so I need something *new!*
Commercial offerings are also fair game... I haven't been paying attention, I'd like to know what exists!
....
*
Before I start a war here: the BSDs remain great, but I've been trying to limit myself to one desktop until now, and that one's dedicated to DragonFly... which remains quite awesome, but it's a struggle to make it play desktop and "development machine" at the same time without getting all tangled up in pkgsrc! Things are looking bright for the future -- Flash is in the process of being opened up, and AMD/ATI are giving backing to the X.org drivers, so things should be on a more equal footing -- but I've got to preserve my sanity in the meantime. :-D And I need to keep up with Ubuntu for work, anyway... :lol: 
