http://www.springhole.net/quizzes/marysue.htm
For those who don't know, a Mary Sue is a character that has none or few flaws, never fails, is beautiful, popular or powerful, a glorified self-insertion of the creator, etc. Often a combination of those. You don't really want your character to be a Mary Sue. In certain cases, if played really, really well, they won't detract from anything, but that's rare. So, here's a test to see how much of a Sue your character is!
Note, the test is very general, as it's made for anything. Roleplaying, fanfiction, all that. There are two RP-specific questions, the rest is made with anything in mind. When the general questions say "written", assume they say "played".
Another note, if the test says your character is a Mary Sue, don't worry. First of all, it's just a test, on the internet. Second, they can be good if played incredibly well. Third, there's always character development.