I've got a couple soldering irons that see frequent use... One is a no-name brand that came in an electronics repair kit that was given to me as a gift from work at one point. Another is a Weller, which sees more use, but only because the thing is blindingly orange and fucking impossible to misplace on my desk
Both are 35W irons, and have worked just fine for me.
I use a 40 watt iron from Radio Shack. It isn't bad, but it takes a long time to heat up.