I've always wanted to hear the road horn original to the 600. Road & Track in their test of the vehicle when it was new mentioned the horn specifically; it was one of two fitted, selected by a switch. They mentioned that the owner's manual warned the road horn is (approx.quote) not suitable for use in built-up areas. I remember specifically, "It sounds like a rhinoceros in labor, and is the only thing we've ever found that can scare a New York cabdriver."
'97 SL500, 40th anniversary edition
'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)
SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)