Rod Hull and Emu spring to mind, so does Oliver Reed and George Best.
I find the problem with Parky (in the later years) and Jonathan Ross is that they seem to re-hash the same guests every series. Its like a best mates club, they don't seem to interview the 'New Kids on the Block' that often.
With the exception of Lewis Hamilton, this last series of Parky was a bit like 'Last of the Summer Wine' which is seen as a resting home for retired actors.
What has Billy Connoly done for the last 3 years or so? Yet every year he's on Parky. Yes he's entertaining but a chat show should be about asking the current celebs the kind of questions the viewers want asking and not the ones their PR Agents want you to ask.
Parky was the master of chat show hosts in his heyday but
IMHO more recently his show lacked bite. It certainly wasn't Saturday night 'prime time' material. Show it on a Sunday after Songs of Praise and the Beeb's equivelant of Heartbeat and it would have been OK.