SilverLexus
Super Enthusiast
I've never gotten anything for free!
Patrick at Excel Detail always includes a peppermint candy.

Seriously, many of the vendors and sponsors have from time to time included samples free of charge. AutoGeek, Poorboys, PakShak, ExcelDetail, SMP, PAC, and others have been particularly generous with deals as well.
My bet is we some more action around the main Spring months as detailing season kicks in.