It really depends what you want. This includes: how you want it to look, what you like on mice and keyboard, which games you are going to play etc. There are some brands that stand out on certain points. I hear a lot that Logitech mice are really good, but e.g. the Razer Deathadder has gotten a lot of positive feedback as well. If I were you, I would try to really make out what you think is important and based on that look around the internet for those specific criteria.
My personal experience: I have a Razer BlackWidow Ultimate Stealth for keyboard which I really like, nice sound, durable, very nice in general. Mouse is the razer Naga with 12 buttons on the side. This one is also handy, especially for playing MMO's but the scrolling...