Keith Moon's "I'm the best Keith Moon-style drummer in the world" is a favourite, but the best that I have heard was someone's description of Boris Johnson; "He looked like an inside-out polar bear that had just been caught ****ing." What about your favourites?
Frankie Boyle on Andrew lloyd webber is the best of all time. hold on till I google it his rebecca adlington one was good too.
A poster on the old 606 (Partick Bateman I believe) referred to a bedraggled Wayne Rooney as "looking like a dejected monkey being asked to leave a sports shop". Made me laugh anyway.