I have a Magnum 870 12 I bought used in about 1973, when I was still in high school.
The only hiccup this gun has ever done is it stalled when a leaky reload allowed a #9 shot behind a shell stop. I'd love to have all of the various shells I've put through it over the years back in my posession. I've used it for trap, skeet, sporting clays, combat games, doves, ducks, geese, rabbits, and whitetail deer (14 or so). I have a riot barrel, standard smoothbore slug barrel, ribbed Remchoke barrel,ribbed skeet barrel, and a Hastings Paradox Rifled Slug barrel with a cantilever scope mount and an Aimpoint on board. If I had to pare the herd down to one shotgun, (heaven forbid!) that would be the one, as there is nothing more versatile, reliable, and extra barrels can sometimes be aquired for a very reasonable price on the used market.

Of the obsolete ones, another sweet pump is the Remington 31. No reasonable way to lengthen the magazine tube, but a very reliable unit. Even pieced-together rustbuckets are some of the smoothest actions there are. I have a field gun someone had a Simmons rib put on that I used at Purdue's Trap & Skeet club when I was a student there that is slick enough to shuck out the shell onto the ground if you were to fire it one-handed at an overhead starling. Extra barrels are harder to get for these, especially with the demise of the good parts on eBay. The single operating rod has never been a problem for me, they always pump. Of these, I have 4 12's and a 20. There are probably 15 or so 31's in my immediate circle of friends. I'm told that Remington dropped the 31 about 1948 or so as too expensive to manufacture. Almost all of the innards are machined. I still see plain ones at gun shows fairly often. A local gun shop had a riot gun for quite awhile marked U.S. and with a flaming bomb.