Josh at South Park Pundit wants to build himself a Scout Rifle. The urge is understandable: A light, fast-handling rifle in a do-it-all caliber is a wonderful thing to have.
Alston has a scout rifle that Bob the gunsmith built. It's a slim little wand of a .308, built on a Remington 600 action, and it handles and points more like a .22 than a bolt-action medium bore centerfire.
Myself, I've fallen in love with early Mauser cavalry and engineer carbines. I have a little Chilean DWM M95 carbine in 7mm Mauser that, despite being a bit on the chunky side for a Scout at 7.5 pounds, is a well-balanced little rifle whose barely three-foot length belies its weight. I think if I was going to make a personal Scout, I'd go for an older small-ring Mauser action and chamber it in .275 Rigby, because I love Mausers. I'd also probably cheat on the weight requirement by going with a Mannlicher stock, because life is too short to own ugly guns. :)