I wouldn't mind having the QB/WR combo if it didn't make me sacrifice other positions - I certainly wouldn't go out of my way to obtain it. The Moss/C-Pepp combo would definitely be nice to have, but you'd likely have to use your first two picks on 'em, thus pretty much solidifying your RBs as among your leagues' worst. The Marvin/Peyton combo is decent - you could even go all out and draft Edge in the first round.
When I look at potential combos, I look at the offenses' scoring potential - basically which QBs in the league are strong candidates for 30 TDs? Here's my picks...
Randy Moss/Daunte Culpepper
Marvin Harrison/Peyton Manning
Torry Holt/Marc Bulger
Darrell Jackson/Matt Hasselbeck
Javon Walker/Brett Favre
...you could even make arguments for these guys...
Terrell Owens/Donovan McNabb
Derrick Mason/Steve McNair
Tony Gonzalez/Trent Green
I don't necessarily try and get the QB/WR tandem on my fantasy teams, but if I think I can draft a solid overall team, I'll gladly take it.