To answer the OP's questions, I rarely tip when getting takeout in Manhattan; the point of doing so is to eat food in the comforts of my apartment and get some exercise walking over to pick it up. I do tip around 10% when picking up from Trattoria Belvedere italian restaurant nearby at least once every week or two, and they're very appreciative/include something extra in my order.
On the other hand, I tried take out from a new Japanese spot in midtown last night, and decided not to tip on a surprisingly overpriced bill ($51 for 2). When I get back to the apartment, the beef teriyaki was very poorly cooked (badly enough that I called back asking for that portion of the check to be refunded on my C.C.), and my girlfriend found a hair in the poorly made edamame that they included "on the house".
Generally, for servers making less than minimum wage, I'll tip 18-20% for good service, 15% for mediocre service, and maybe 10% for absolutely terrible service, but that's very rare.
For bartenders I'll similarly tip 10-15%, depending on where and what's ordered.
During the days of filling up at Exxon and 7-11 in central NJ, I would sometimes tip a dollar if the attendant was very attentive/prompt and careful in filling up my cars; my cousin worked many nights/weekends doing this and appreciated every little bit. At Costco where I may wait 10-15 minutes in line just to fill up during the day, no tip.
My dad and I do oil changes, tire rotations and other routine maintenance on our cars. But for more complex/labor-intensive engine and body repair work (which my dad did in the '90's as a mechanic), a tip is appreciated.