I bike to get car parts every time! So glad to hear others think this is hilarious!
On New Years I got into my car to drive 2 hours to my friend's place and it was totally dead. I popped the old battery out, strapped it to my bike rack, got a discount for bring the old one in, and then biked home with the new one. It all took only like 20 minutes and I made it to the party. Way better than getting AAA or some crap.
Other good ones are driving your car to the shop with your bike in the back, dropping it off and then biking away. I bring two sets of keys and tell them to lock one of them in the car so I can pick it up after hours too. I also have bike to get a Uhaul several times. It's perfect. You bike there, throw the bike in the back of the Uhaul and then do the reverse when you're done. No bothering people for rides or taking the bus or anything.