I can't help myself - when somebody lets me in (or I cut them up: the difference it sometimes in the eye of the beholder...), I stick my hand up. I've been told it's just endearingly quaint, but in a mocking voice.
That's not to say drivers here aren't very accommodating. Not at all - they're great, they'll pretty much always let you in. Nobody's going to sit blocking you deliberately for five to ten minutes and totally ignore you for that time. At least, I've never seen it.
Also, nobody beeps their horn here. Or, very rarely. In that sense, it's a lot like home.