What's a good party game to buy for adults?

Depends what appeals to you and the group. There is Skull and Roses, Dixit, The Resistance, and Telestrations. All I can see easily working in a tipsy party environment well. I would check out YouTube videos of game play and see which one appeals to you. :)

Left Center Right

"Adult" games need not be risqué or provocative to be fun. A Bingo social could be very exciting, especially when there are a lot of prizes at stake. This game of chance evokes people's competitive nature.

Put a twist to it by using the letters Qw, E, R, T, and Y instead of B, I, N, G, and O. Your prizes should be inexpensive yet quirky, like a set of Mickey-Mouse-printed neckties, a pair of rainbow-striped socks, or something practical, like a gift check, discount coupons, or movie passes. It could also be chocolate bars. ;-)

Monopoly played with staff of a brothel, if they will never buy houses or hotels otherwise,

all make for a keen if scantly clad gaming group. Its how I escaped an orgy in-progress.

Monopoly or Beer Pong

final fantasy

Deck of cards, and then play strip poker!!!!!!!!!!!! Very fun!!!!!!!!!!!!!!