If it were me, I'd buy a Marlin 1895GS, stainless guide gun in .45-70 (+P or "Marlin" capable if you reload). Tips in at 7# empty (catalog, mine's 6# 9oz. empty without the glass), which isn't incredibly light, but the ease of handle that the 37" overall length gives more than makes up for the extra pound over other "lightweights"...I'd much rather carry a heavier gun that's easy to manuover than a light rifle that gets caught on brush/limbs, etc. . The levergun also lends itself to easier carriage than a bolt gun, wrap your hand around a marlin levergun's action sometime and you'll understand.

If you're set on a bolt gun, I'd buy a WSM in a compact, I don't know who offers one, but the WSM's are an awesome combination with compacts...I'd either go .300WSM or 7mmWSM.

I don't feel that most lightweights, like I said, really offer that much advantage over standards, they weigh a little less, but they're really no easier to handle (only usually 2" shorter and 4-8oz lighter, occasionally a full pound), compacts offer usually a pound at least lighter and 5-6" shorter).