I second thisHeh. I never thought about this. That is a genuinely nice sentiment.
Here's my thoughts after thinking on this a little. If it is your sales guy who does it for you and brings you the keys, don't tip him. I do this all the time for clients and I'd much rather you give me all 10's on the survey Infiniti sends you than tip me a couple bucks.
If it is someone in a uniform, who works in the detail department, by all means give them a tip. They'll love it. I've never seen a client tip one of those guys. They work their butts off in all weather and get very little recognition.
In a sense, I tip our detailers once in a while. Not directly, but whenever we go for a beer after work, I invite them along. If they come, I pick up the tab. But they'd much rather get a tip direct from you than an occasional free beer from me.