..get W2G's for slot wins of $1,200 or more, regardless of the bet.
Keno wins of $1,500 or more, but the bet is deducted.
Example:
Bet $1, win $1,500 = no W2G.
Bet $1, win $1,501 = get a W2G.
No W2G on table game wins.
Losses can be deducted from W2G wins when you file your taxes at the end of the year.

In NV wins of $600 or more from poker jackpots require a 1099.
In NV, some poker rooms follow the Binion's Closing Agreement for tournament wins, some do not. (W2G on wins of $600 or more)
IMO all should follow the agreement. My CFO is in dis-agreement with me. He wins.

Foreign winners witholding is 30% depending on the country they are from and if their country has a tax treaty with the US.
Example:
England, Germany, Italy, etc have tax treaties, no witholding.
France, no treaty, hold 30%.
Denmark tax free $3,000 and under, 30% held on all over $3,000.
Foreign witholding is very complicate. Each country can be different. Tax treaties for any given country can change from year to year.