I have Testament and Trojan War, but haven't had the chance to play them. Testament looks great, though, and really is different from just about any RPG I've seen. They really made an effort to evoke the mood of the setting.
The game I'd like to have is Ringworld from Chaosium. I like Larry Niven's Ringworld books, as well as his Known Space setting in general. The game I've heard is a really good adaptation, and has a lot of cool reference material that would be of interest to non-gamers. Over the past 20+ years I've tried to track it down, but the only times I've ever seen it for sale is on eBay, and it always goes for way more than I'm willing to bid.