Postal 2 - old but if you download it for free as a torrent it's a fun game to play. You can piss on people and stick the barrel of a shotgun up a cat's ass to use the cat as a silencer. you can feed cats to dogs. you can pour petrol on someone, light them on fire, let their skin burn off then piss on them so they are like zombies crawling around on the floor. you can throw scissors at people. you can go into peoples houses and hit them with a shovel and make their head come off. you can shoot gary coleman.
it also dosnt sound anything like portal 1.. im assumeing half tha shit you said you can do in tha game are mod's people made, right?