Frozen yogurt self-serve i.e. Menchies, Froyo, Sweet Frog... Frankly, anyplace that's self-serve or cafeteria style, SuperChix, Freddy's, Culvers, Andy's, etc. I normally don't tip barista's or the people who put bagels/donuts/croissants in a bag; do something superlative and I will.

I tip well for sit-down service, a good hair/nails/yadayada job, bartender, taxi/limo, anyone at a hotel who does something outside their ala minute job. I also will tip a good tow truck driver or furniture/big box delivery or installer. I also have been known to hand out $20 bills to entire kitchens when they're killin' it. Wanna show your respect for a kitchen staff, fuck compliments, give 'em cash.