My biggest and most popular game (for varying definitions of popular) is Fastlane, the one and only roleplaying game to take advantage of all things roulette. Beyond that, the only other thing I have in print is Snowball, a free downloadable game that was based on The Pool (link unavailable), once a popular game in the indie community.
After Fastlane I sort of rested on my laurels, and couldn't really find much new to design, at least nothing that simultaneously inspired me and gave me something to grab. For a while I tinkered with a game I called Ensemble, a fully playable GM-less game inspired by Prime Time Adventures that I never could get quite where I wanted it.
My most downloaded game is Creeks and Crawdads: Reimagined, which the author pretty much gave me free reign to play with. It might very well be my truly most popular game. It is based on the original Creeks and Crawdads game from long ago, and inspired by it, but remains a totally new approach.
Beyond that, there's a lot of stuff on my website in the Atheneum (which is sort of a half-bakery of semi-finished rpgs, I haven't added Ensemble yet because I have hopes that we are still in its development phase), and some rpg hacks in the Game Twists section. My proudest creations in that section are the tweaks to Nobilis and Everway (although my modifications to Rolemaster have a place in my heart too).
Like a lot of us, it was modifying other game systems that sparked my designing, and a lot of the more recent changes and tweaks are still available on my website. And my first game published was Snowball, which was a modification of an existing game. I still think I was halfway crazy when I tinkered with "Size and Density as statistics" for the HERO system.
Feel free to post about any of my creations and/or modifications, if you want to comment on them.