I tip the pizza guy, chinese food delivery guy and even my lawn guy (his tips are usually watermelon and/or water/beer). I also tip the waitress when I pick up my food on a "to go order." Heck, I even tip the furniture delivery guy.
I delivered flowers for my high school ex-girlfriends mom during the holidays many, many years ago. Most of my tips and biggest tips came from middle to lower income people. The least amount of tips I got came from the wealthy (multi millionaires). i'm not saying they're arsholes, just saying they didn't tip good, hahaha.
People I don't tip
Mailman, not even at Christmas either.
Dog groomer. The lady charges too dang much as it is.
Garbageman
I am a more than generous tipper but I won't tip on booze that the wife orders during dinner. A glass of wine runs 8-10 bucks a glass. The waiter carries it from the bar to the table. Heck, he didn't even pour it. I'll tip on the booze as if it was a 2 dollar pepsi/tea.
I also hate forced tips, such as gratuity included with 6 or more persons. The waiter usually would have made more from me without the tip added. (sometimes i'll give more but not always).