For slot jackpots of $1200 or more they issue W-2G. For slot tournaments they issue 1099. The W-2G is offsetable up to losses, the 1099 (unfortunately, for the non-pro) counts as ordinary income.
You can deduct expenses off the 1099 by filing it under a business schedule C if you gamble quite a bit. My parents (both accountants) do this with very little issues. You of course have to keep aware of the hobby vs business aspect of schedule Cs, but thats over the course of several years.