Looney Labs makes a card game called Aquarius. I really like the artwork on the cards, but I find the game a little too random and chaotic for my tastes. So I started trying to come up with alternate games that could be played with an Aquarius deck.
The first game I thought of, in November 2002, was inspired by Carcassonne, using Icehouse pyramids. It eventually evolved into Quintazone, and I think it's a pretty solid game.
In January 2003 I started kicking around the idea of a trick-taking game, vaguely inspired by Xactika (which has multiple suits on each card). I posted the idea to the Aquarius mailing list but didn't get any response. I never actually developed this to the point of being playable, but it's still rattling around in the back of my mind.
In March 2003, after showing my Carcassonne-inspired game to Greg Lam, he came up with an idea for a racing game, also using Icehouse pyramids. I don't know if we could recreate it but I might ask him one of these days.
In November 2003, I came up with a deduction game called (what else?) Elementary. It's similar to Clue, Sleuth, or especially Black Vienna.
There are several other games using the Aquarius deck listed on the Aquarius instructions page, but I haven't tried them. Pantopia looks the most promising, but I think it's still an unfinished design awaiting further playtesting.
If you have or know of any other game that use Aquarius cards, send me mail and I'll add a link to it. Actually you'd probably be better off sending a link to Looney Labs so it gets onto their Aquarius page, but if it's particularly cool I may single it out on this page too.
I have invented a few other games that don't use Aquarius cards.