TOS - Kirks stunt double (no lie, he kicked another stunt double square in the throat in the episode "For the World is Hollow and I have Touched the Sky" (a little after eight minutes in) and knocked his goofy hat off--one of the best moments in the series for me special effects wise)
TNG - Data
DS9 - Plain, simple Garak
Voyager - EMH
Enterprise - Didn't watch the series much (maybe two episodes... :S)
TOS: Spock » "Excuse me, there is a multi-legged creature crawling up your shoulder." - Stuck with me for life
TNG: Jean-Luc Picard » Damn good actor - FACT lol
DS9: Sisko » (Just think Avery Brooks is bad a** )
VOY: between The Dr / Seven (no one else stood out for me.)
ENT: Archer again no one really stood out.
STXI: McCoy » Just made me laugh all the way through!