The best crooked gimmick I've seen was at the Country Inn in Calabasas, California, which notified me about a phony "energy surcharge" at check-in, and made me sign something accepting it, before they let me into the room. Was I going to fight it, arriving tired at midnight with no other place to go?
Another great scam is the "voluntary" UNICEF donation added for years at European Sheraton hotels. Yeah, you can get it removed, and deny starving children their last shred of breadcrust, hah! Rest assured that if the donation is presented to UNICEF, Sheraton takes all the credit.