Yeah, one opinion for every hunter.
I shoot an old Ithaca 37 pump (1958 vintage) 12 ga 2 3/4 full choke.
ONLY with bismuth or tungsten-you don't wan't to put steel through an older gun like that.
My alternate is a Browning BPS 20 ga. I only use it on ducks / geese over decoys-no shots over an honest 30 yds. and it's deadly, but I can't recommend it as an all around duck gun.
One of the BPS 12's might work for you. And I love the top-tang safety and bottom ejection (M 37 is also bottom ejection).
With the collapse of Ithaca this past summer, I'm guessing you could find an orphan 37 that some dealer wants to unload cheap.
Unless Ithaca revives, factory service will be a problem, but there are literally hundreds of thousands of them out these, and parts are readily available.
I found that switching from a double to a pump improved my shooting dramatically, because it forces you to pump and consciously follow the bird, rather than just blast away with a double (really a two shot semi) or a semi.
That little 20 is also my pheasant gun, and, once you're used to it, very fast.
I got a triple on pheasants with it this fall, and by that I mean 3 cocks in the air all at once, and five seconds later, all 3 on the ground, graveyard dead....and believe me, that's the gun, not any skill I might have.
Besides, pumps are infinitely reliable. My buddies all use Rem 1100's. Great when they work, but high maintenance, and if you don't clean them religiously, like any semi, you just bougt a pretty, and very expensive, single shot. I've seen too many hunts ruined by finicky semi's.
SAFETY FIRST: RELAX!!!
There's lots of birds, and you don't want to have to explain to your buddiy's wife that you just made her a widow.
Control the muzzle, and check the safety.
Your life depends on it, and so do your buddies'