Caedmon's Call.. but keep latter guitarist Andrew Osenga, too.
Sound of Contact (If Simon Collins and Dave Kerzner can get along)
Spock's Beard has already had a few get-togethers over the years; but I'd like to actually ATTEND one of them!
Led Zep - sure!
Triumph (yeah, they did it about 5 or 6 years ago, but I missed it)
Roxy Music - not just at the RnR HOF
Iona (with Nick Beggs on bass/stick)
Genesis - with Gabriel AND Hackett
White Heart (preferably the Florian, Gersmehl/Smiley/Wooten/Sallee/Knox lineup)
And as big of a Marillion fan as I am, I really don't want to see a reunion with original frontman Fish.