Well, at least you can log it.
Longest I've ever had to wait for takeoff was actually at an uncontrolled field - 45 minutes, but no other traffic in sight! Weather was slightly less than VMC, so I needed to get my clearance on the ground, but the airport was close enough to another airport that they couldn't release me. I had a phone line open to FSS, who kept putting me back on hold, saying I needed to wait a few more minutes, etc... On the 2nd or 3rd time we were talking, I asked what was going on and they told me it was another plane doing approaches at another airport.
Come to find out, it was a Beechjet of all things! Who shoots practice approaches in a jet anyway? So I sat and watched my ADS-B until I figured out what airplane it was and where they were, flipped to the CTAF for that airport and asked if they could please knock it off long enough for me to get out.