Well, there's all the different types to remember. For example, Cat Janet is supposed to be weak to Fighting types - Cat Janet?

[She's run off! There she is way up ahead, much larger than she was like two days ago.]

She's been doing that lately...anyway, I would think most things are weak to getting punched, but that's what the books said. Birds are good against Fighting types, though, so I have Quaver for that if it ever comes up.