One person who rarely gets mentioned in the guest wants: Dan Castellaneta (Would be COOL 'cos he's Homer Simpson, too!!!!)
Other wants include: Robert Carlyle, Claudia Black, Ben Browder, Christopher Heyerdahl, Chris Judge, Dan Shea, Cliff Simon, Mel Harris, Gary Jones, Beau Bridges... (this isn't an exhaustive list - anyone from Stargate would be great - even the ones I've already met!!)
Oh, and if RDA or Amanda Tapping were to turn up, I guess that'd be okay....