M.F.
Definitely the Baby Bjorn plastic potty.
It cleans up soooooo easily. It's a little bit more expensive than other potty chairs, but the easy clean-up is worth 10 times the price. You put the insert in backwards for girls (so the shield is in back) and turn it around or boys. My daughter used it successfully when she was training and now my son (23 months) is using it.