I came across some really great guerrilla advertising campaigns used on buses. One is for a Baltica Beer. The poles to hang on for people who stand in a bus, actually have beer cans around them. So when you hold onto them, especially in a group, it looks like everyone is holding a beer.
Another cool guerrilla bus campaign i found was for a brand of watches. The straps people hold onto, similar to the poles, actually looked like watches that you could slip your hand into. When people hold onto the straps, it actually looks like they are wearing the watch.
I just thought both of these ideas were very clever, and could perhaps give us as advertisers, a little bit of inspiration when thinking of our next guerrilla tactic. Enjoy : )