Writing Forum

The world is full of writers who identify themselves as pantsers. Steven King and George R.R. Martin are probably the most famous examples (yes, those intricate plot lines in ASoF came about without an outline).
Really though, I think the important thing isn't whether you're a plotter or a pantser but that you have a nice mental representation of your story so yo don't end up meandering through the pages. This means, as Sir Various pointed out, knowing your story structure types and when to deviate from them, but also knowing what sort of trouble your protagonist might get himself/herself into.

Most people probably aren't strick outliners or pantsers anyway but fall somewhere in between, and, again as Sir Various said, everyone should try a little of both.
I'm more of an outliner myself, for example, but I never do character sheets. I might do some freewriting from a character's perspective to get a sense of their voice though.

I would suggest watching some of Brandon Sanderson's lectures from BYU on youtube and/or writeaboutdragons.com or listening to the writing excuses podcast. He has good, concise explanations of the advantages and disadvantages of both plotting and pantsing and talks about how you get some of the best from both worlds.