Garry's mod is a sandbox game with infinite possibilities. I say infinite because the community has made over 1,000,000 (1 million) mods/addons! Also, this game is multiplayer! Totally worth $5!

Valve's game made in 2004, has been very successful. This game is a singleplayer game which I have personally played and it is as fun as fun can get. The best thing is, is that it was made in 2004!

This game is very fun and definitely worth $15. It has several different gamemodes, but casual is the most popular. Be warned! There are very toxic people in this game! Be careful and have fun!