Great nickname for masculine names ending with -in, but I wouldn't use it personally as someone's real name, because it doesn't really fit. Although, I probably am biased since this is my personal nickname.
The comics and movie are good, but I wouldn't give this name to a child unless it was a nickname. I think Tintin IS his nickname, and his real name is Martin, Valentin, Augustin, Justin, or his last name might be Austin, Burtin, Kentin, Coltin, Miltin, or Ashtin and he used Tintin as his pen name, since he's also a journalist. Also, I think his name should be TinTin instead of Tintin if it is a nickname. Guess we'll never know though...