Like MumbleSquad I haven't seen any good ones lately on cars, but this being a seaside town, I have the opportunity to scan them on the racks next to the kiss-me-quick hats. When I find a good one, I add it to my list of one-liners. Luckily, we seem to have grown out of the "windsurfers do it standing up" genre, they tend to be wife/girl/boy/in-law or motoring related these days. I think I saw these as bumper stickers but I can't be sure. Many of them are recycled quips and quotes anyway.

Jesus saves, Moses invests, but the Mongol Hordes

My ex-wife's other car is a broom.

Polygamy - too many wives; monogamy - the same.

Teenagers - your punishment for enjoying sex.

They also surf who only stand on waves.

Rod