How it affected me: Mr Wobbly Hides His Helmet. Many, many hours of enjoyment. But it also got me into trouble on a few occasions.
The game that changed the way I think: Go. I even got my first great job because I beat someone at Go, so he thought that meant I was smart. He was the hiring manager for a project that required international travel and which gave me high visibility within the company. But what it really meant was just that he wasn't a particularly strong Go player. I'm still an OK player, though one of my sons now plays at master level (which, he says, means that not all 12-year-old Koreans can beat him).