1Up has a phenomenal list of the top 101 best games in the indie marketplace, all of which are your for free. The majority are action shooters, but there are a few more "serious" options, including Disaffected, dedicated to harassed Kinkos Copies employees everywhere, and I'm OK!, a game made to Jack Thompson's personal spec.
The Wikigame, unfortunately, didn't make the cut.
Get 'em here.
