I was once belligerent enough to leave service advice as a tip, in a small brewery tasting room that does not provide table service and requires patrons to visit the bar for their drinks. My wife went to the bar, and there was nobody there, so she came back without (my) beer. Just then, the bartender walked past our table, she tried to order me the beer, and said she would have to go to the bar for service... anyway, the guys at the bar took my "tip" and contacted me on facebook (by my name on the credit card, i assume) and suggested that next time I was in, they would buy me a beer for any hard feelings. They also made it clear that my "tip" was not fully coherent... and that they did not mean any offense, which I had obviously taken.
I am not really sure where I am going with this... but, I never had the balls to walk in and ask for the beer they had offered... Probably because when I told my wife about it the next day, she made it clear what an ******* I was being that night...
Clearly I enjoyed their double IPA...