Being in the traffic side of the biz I'd have to say it would help to know what kind of traffic you're looking for, that would help me make a better suggestion.
That said of course
www.madisonavenue.com (no ref code but I do own the company so I guess that's the same?). We've got tons of straight, cam, dating, decent bit of gay traffic, and some tranny.
TrafficDude is rock solid. Good people behind that outfit. Tons of gay traffic.
GTSAds.com is from GTS and they've got tons of traffic from TGP/MGP world.
If foreign as a few folks have pointed out Eros-Advertising has a great rep.