Okay, after a week off because I did the poll, back to this.
This is a tough one for me because I don't get a ton of inspiration from keyboard players. I didn't realize it until I started thinking about the thread. There are people I respect, and people I wish I could play like. But for inspiration, it's Elton John, Tori Amos.
And in an admitted bit of a cheat, the most inspirational is Mike Keneally. It's a bit of a cheat because he's an incredible guitarist and just a great musician overall. He played guitar and some keys in Zappa's final touring band in 1988, but after establishing his solo career and his place as a guitarist, he's gone on to play keyboards for Satriani and Chickenfoot, among others. He even did, at Steve Vai's request, a solo piano album of Vai's material (and is working on a second).