What is the best Adult game in Steam ?

1. Bad Rats
2. Bad Rats GOTY
3. Bad Rats Scat Edition
4. Bad Rats Blue Waffle Pack
5. Bad Rats BDSM Pack

Postal 2

putt-putt saves the zoo

Depends. By "adult" many people think of gory and sexually explicit stuff because you know, you have to be adult to play them, but these stuff hardly turn out actually adult (Postal 2 for example).

Or there are stuff that you need to be mature for, like This War of Mine (I haven't played but what I've seen you have to be emotionally mature to deal with the game),

1- Call of Duty®: Advanced Warfare
2- how do you Do It?
3- GTA V
4- Gender Bender DNA Twister Extreme
5- My Ex-Boyfriend the Space Tyrant

Barbie's Dreamhouse, duh.

1. Skyrim with nude mods
2. Sains Row 3 with nude mods

1. Saint Row series.
2. Postal 2.
3. Hunie Pop.
4. South Park: the Stick of Truth.
5. Plug & Play.

The Witcher games have a lot of things ;)

The Blackwell series (Legacy, Unbound, Convergence, Deception, Epiphany).

Harvester.

Define "adult game".