1. Rental Car Van driver: Yes, $1-$2 if I am helped with bags. No otherwise.
2. Checking bags curbside. The only reason I would use this if I had a lot of bags, which means the skycap has to handle them. This being the case, yes, minimum of $5.
3. Starbucks--NO. The coffee is outrageously priced, and it's not table service. I resent the presence of the tip bucket most of the time. However, if I don't feel like dealing with loose change, I might drop that in the bucket.
4. RCC-Yes, if using a coupon or ordering a paid drink and sitting at the bar. NO if just asking them to pour me a coke. (IMHO, soft drinks should always be self-serve anyway)
5. Taxi-Yes, around 10%, or round to nearest conveninet bill denomination.
6. Flight attendants-Adament NO. Where does it end? I resent the guys who hand out chocolate, too; if the practice increases, then it will force the rest of us to do it, too. I read somewhere on another board that airlines thankfully prohibit FAs from accepting tips.

I wish someone would lead a tipping revolt in the U.S. The rest of the world doesn't do it to the extent we do. Now if we just all band together, we could put an end to it, too....