I'd like to cheat and pick the H&K G8. It can be used as both a SAW/LSW/LMG and as a marksman's rifle. I saw some pics of it being carried by German KSK commandos and fell in love with it. It's a wee bit munchkinish but I built a PC around the gun.
The following is an excerpt from Wikepedia:
"The German Army, German Navy and the Federal Police use a variant of the HK11 designated the Gewehr-8 (or G8). It is tapped for telescopic sights and has a quick-change barrel with a bipod that uses either a heavy match-grade bull-barrel or a heavy barrel for automatic fire. It was designed to use G3-type 10- or 20-round box magazines in the designated marksman role, but could also use a special 50-round drum magazine for sustained supporting or suppressing fire. The modified G8A1 adopted the improvements of the HK11A1 series and was only able to feed from magazines and drums."
It's listed as the HK 11E under German machineguns on Paul's site.
Sweet.