My all time favourite is "It is difficult to explain to white mice that black cats are lucky!". another old one "Preserve wildlife-pickle a squirrel". also "Yea though I walk through the valley of the shadow of death I shall fear no evil---For I am the meanest S.O.B. that ever walked in the valley."
"Sado-masochism means never having to say you are sorry1"
"Traffic wardens are nice people---p.s. back in 5 minutes!"