Not sure if it's been suggested, I started skimming halfway through, but LAUNDRY. Make him do everyone in the house's laundry - wash, dry, fold, put away. To me, that's the worst tedium, and definitely the most time consuming.
If you want to be really evil, just make sure you go over every chore you ask him to do and find something wrong. Make him re-do it, even if it's just one slat of the miniblind that got overlooked. Another thing you can do is re-sweep after he has, and take as much time to do it so you can gather every spec of dust he missed. Put it in a pile somewhere where he can see it, with a note of how much of a failure he is. Also, time limits to get tasks done add an extra dose of anxiety and pressure.
I have plenty more. My step-mother was the queen of chores and punishment for imperfection.