RE: Which guns to collect?
Ewww.
I would stay far away from limited edition or commemorative firearms. They are way over priced, and for the price you are just paying for a serial number range and some cheap gold filled roll stamps.
The Springfield D-day Garand is a farce. Why pay $1300 for a replica in a fancy box when you can buy the real deal that has actually been there and done that for about 1/3 the price and which will always appreciate in value?
I see tables full of commemorative rifles at gun shows for sale, but I've never seen anyone buy one.
The only special editions that are worth buying would be Winchester 1 of 1000 rifles when offered.