I'm a lefty, but I actually use a mouse in my right hand!
Not fussed about wired/wireless. I'm only going to use the mouse for LAN parties, so a wired one might be more portable, i.e. no little receiver thingy to lug about.
I have a Logitech MX1000 (I think that's what it's called!) which I'm fairly happy with, as I say, I just want one to stick in a bag.