Bilsteins 4600's. Put them on my 2005 F250 Powerstroke at 60,000 miles. Made a world of difference. I tried to get them through EShocks, they said they had them in stock. They didn't, waited a month for them to admit it and give me a refund. Got them from Shock Warehouse. Easy install.
Going to put a set on my 2011 F150, the OEM shocks are getting sloppy at 60K miles. Then I found out they were a strut-type shock in the front, and have to take apart the ball joint and drop control arms and basically take the front apart to get them out.