I will beta for any story type and pairing, but I'd prefer it to be from the original section. I'd hate to fail you by not being able to recognize that Ron Weasley is acting out of character or something like that. If you send me a Harry Potter or Buffy story then please know that I'll only be useful to you with correcting spelling and the like.
If you choose me as your beta I'll help with any grammatical errors to the best of my ability. I'll also give my opinion on the plot, style, etc of the story. What I won't do is force my thoughts on you. I am fully capable of realizing that you are the author and my suggestions are only suggestions.