Worst:
A: Cutting and assembling blinds. Owner had a seriously "improvised" cutting rig with cut line marked with a marker. Put 5 sets of blinds in the rig, and you'd get 5 different cuts. Far from a precision device. Training was pathetic, expectations were high.
B: Sales for phone company. Job wasn't bad, but co-workers were the most closed minded idiots ever. I could have had more open-minded conversations in a medieval hamlet in the year 1039 AD. I've literally been in better social situations with animals.
Best: Being a business owner. I don't care if I have to go to the warehouse right now to fight off Utahraptors with a chainsaw. At least I'll know I did it for myself and my employees (who are the greatest), as opposed to some jack holes who I don't even know.