In issue #186 of Fine Woodworking, Gary Rogowski had an article where he listed the ten essential router bits. As I remember, there was some controversy (as well as a run on woodworking stores) about the choices. Every one had a half inch shank. FWIW, the list included:
1/4 in. straight bit,
1/2 in. straight bit,
3/8 in. spiral-fluted straight bit,
rabbeting bit with four bearings,
1/2 in. dovetail bit,
1/4 in. roundover bit,
3/8 in. radius cove bit
45 degree chamfer bit,
three-wing slot cutter,
1/2 in. flush-trimming bit.
This is certainly overkill, but should start some controversy, which means more knowledgeable souls will weigh in. For starters, I think a couple of straight bits, a roundover, and a flush-trimming bit would make sense. Maybe a rabbeting (I think you call it rebate) bit and chamfer bit would be nice to have. I would also go for 8mm bits, where possible.
So, what do the real experts say?
Richard