RA231 - made a hissing noise most of its life, revved incredibly high before changing gear. Heat downstairs, and a lot of black dust on the back seat
RH106 - the slowest RH in the fleet by a mile!
RH13 - the smokiest RH in the fleet by a mile!
RA196 - the smokiest RA in Ringsend, continually covered in oil at the rear
RH7, the first RH I was ever on became very unreliable in later life, and I was left stranded twice before it was w/d. Drivers knew it was dodgy too.
RA284 - 298 were all a no go area for me for most of their lives. Continually filthy and covered in graffiti.

Bus Eireann
I hate the seats on the VG's, so all of them are no go for me. I actually like the interior design apart from that though
I didnt like the VC200's, found them cramped.
Could mention a couple of BE contractors I dont like either but I wont!