The 9mm Glocks will bring the biggest "return on investment" in today's market, and are arguably the easiest to replace, should you decide you need new versions later. I wouldn't part with an FAL of any flavor (assuming it's reliable and accurate) unless you've decided definitively you're completely done with them. The Mk23's are always unicorns - worth big money to the right collector, very hard to replace. The market on other HK pistols is hit and miss - not sure you'll see a lot of return there.
Any/all of those revolvers should bring a nice return, especially if you posted them here (hint, hint).
PS - Dibs on the WC GP100