d20 Transformers (just needs rules for making them, and good vehicle rules, and you're all set)
d20 Masters of the Universe/Princess of Power (He-Man and She-Ra's worlds would make EXCELLENT gaming grounds, and this would be your chance to a make Skeletor and Hordak TRULY menacing!)
d20 Pokemon (I personally LIKE the Pokemon games. As long as the RPG stays true to the games, then it would be great to play. It would also serve to pull in younger gamers, who could 'graduate' to D&D or whatnot.)
d20 Princess Bride (My favorite movie of all time... How I would LOVE to just have a sourcebook with geographical information, plot, NPCs, and story hooks, etc. It just takes one book!)
d20 Spaceballs (Another that would just be a sourcebook. Hell, just hook it up with the Dragonstar books for basic rules, and include races, classes, new vehicles, weapons, NPCs, and of course, the Shwartz!)
Chris