Well, I'm going to cheat here and use the English version of my name, since there most likely isn't a single video game character named Valtteri. So, Walter. Well, there was one minor character in Dragon Age 2. I think he was the son of an insane mage. There's a Walter in Megaton in Fallout 3 and a couple Walters in New Vegas. No major characters spring to mind. Okay, except for most player characters, but I don't think those count.