Gauge is not the biggest factor when I am buying guns as a collector piece but I have upland hunted almost exclusively with a 16 gauge for the last 10 years. When I find something that I really want if it is a 16 gauge that is a bonus and I will definitely use it the first chance I get.
I recently bought a custom engraved Citori Gran Lightning with Browning Custom shop style D5G deep relief engraving by Ron Reimer with 3X wood. Being a 16 was a closer for me.
It is a 16 gauge and has 28 inch barrels with choke tubes. I like everything about it except the plastic butt plate is kind of cheap compared to the rest of the gun. I'll have to take care of that soon, most likely with a leather covered pad.
Here it is below on its first outing just the other day.
Ron Reimer is exceptionally talented. Here are some close ups: