My most consistent wage has been $1/year-old. I once tried the commission system, but it was like a second job for my wife, and we nixed it.
More recently, my two teens have been doing a really terrific job, so when I have the cash, I pay them $20 each week, and the younger ones, who do a really good job, too, now get $10 each.
I have added the following a la carte payments: $2.00 for every load of dishes (empty and load the dishwasher), and $0.25 for taking out any full bag of trash and replacing it (whether kitchen or bathroom or office; if it's full, take it out, and grab a quarter from the change bowl).
One daughter heavily embraces the dishes option. She'll tally them up and cash in some for a $20. One of the younger ones has been taking out the trash nearly every day.