Making it a little more specific, I'd go with the Barrett 98B in .338 Lapua. That would take half my money. Maybe I'm dreaming, but I could probably get a glass good enough for me for $2000. The remaining $3000 would buy 500 rounds, since I'd be buying in bulk.
That's all.
/ That or I would go buy a bigger safe, Wildey Magnum, new muzzle loader, a nice O/U and SXS, a couple AR's, an AK, some ammo and if there's any money left I suppose it would be just what ever catches my eye.