William (from the German Willhelm), meaning "Valiant Defender." You'll also have the versatility to be Will, Bill, or Liam if you like. You might be able to squeeze Willem out of it.
Having lived with it for the last 29 years, I can assure you that it is quite a nice name. Also hard to make fun of since it doesn't really rhyme with much, though that's going to be less of a problem for you as an adult. Billy and Willy can be a problem, but some people actually like those variations too.