Wendy's/AirTran promo was fun. I had 4 Wendy's on my way home from work. For about 3 weeks, I stopped into each one on my way home, grabbed the cups off the top of each garbage can inside, and rinsed the cups out in their bathroom.

After about 3 weeks, two of them asked me to stop, but by then, I had enough for 14 round trip tickets.

Best stop was when a customer asked me what I was doing. I explained. Turned out she was there with a large group of students. As I'm walking out, she made a big announcement to her whole group to save their cups and turn them into her after they finished eating.