I play poker for a living. I live in California but made a tournament score while I was staying at my parent house in Wisconsin. Do I pay the money I made in that tournament to Wisconsin state tax? It would help me financially since Wisconsin state tax is less then Californias.

Yes, you need to file a WI tax return, since that is where you earned the money. The bad news is that it really won't save you anything, as you must also report the income to CA and calculate a preliminary tax bill using CA's rates. Then you subtract a credit for the amount already paid to WI, so the result is that you end up paying a bit extra to CA which is the difference between WI's rate and CA's. Unlike gambling - when it comes to taxes you can't beat the house!