Tough question...
Geez, I can't think of anything really expensive that I think I would really enjoy.
I'd say, for ordinary Title 1 firearms, probably a high-end AK in .223 with 16" barrel, Vortex flash suppressor, and an Aimpoint or Kobra, but probably on a standard stamped 1mm receiver for lighter weight, with an M4 style adjustable stock and a detachable light, plus mags, a lifetime supply of ammunition, and tuition for a few carbine classes. Or, perhaps a really, really nice Remington M700 in .308 or some moderate long-range cartridge, with the tactical style ergonomic stock and a high-end Leupold or something sitting on top.
I'll also take a side order of Bersa or Beretta small .22, a Seecamp .380 with aftermarket Trijicons, a Glock 17, and a medium-frame .357. And a bigger safe.
Title 2/Class III stuff? I'd love to have a reproduction DeLisle (sp?) carbine (cut-down bolt-action Enfield in .45 ACP with integral suppressor, modified to feed from 1911 magazines), because I read an article about them once and thought they were really neat. And, unlike Class III automatic weapons, I might could actually
afford one of those someday...