I steered clear of first-person shooters though I did play the occasional DOOM when I was younger. It's worth to try that out. I want to try out the mods someday, particularly the ones with Mario on them.
My favorite first-person shooter is definitely Left 4 Dead 2. The only reason I got it was that the Mario mods were hilarious and the hammy voice acting sealed the deal for me. I got into the game pretty late because initially, zombies just didn't appeal to me. Too violent and too gory and scary. The game freaked me out a bit, and I still remember hearing swears in the game surprised me as I was really accustomed to "cleaner" language in games (at the time)/ The gameplay is really solid. And the genre it has, being an asymmetrical co-op shooter, isn't that common on the market, but demand is there. I want to try out Warhammer 2, Vermintide, which is described as Left 4 Dead with a melee focus (and it also has deliciously hammy voice acting). I also heard about Earthfall, though that one seemed to be disappointing for its lack of content and its rubbish sound design. Yes, Left 4 Dead 2 also doesn't have much content, but it has mods that add on so much to the game, including new maps, and they're all free.
So, I'm currently playing Left 4 Dead 2 a lot and our version is a weird experience.
Payday 2 is another co-op shooter though I'm not sure if it's similar enough.
Another game I go back to is Goldeneye: Nightfire, mainly for the multiplayer arena. Fun. We like shooting Jaws to death, and the Sentinel Missile is always fun to use, especially against the dumb bots in the snow level.
I think there's a bit of Overwatch players here and maybe some Team Fortress 2, though I myself am never big on arena shooters.
Anyhow, my favorite gun so far is the sniper, for the noise it makes and the scope is fun. Between shotguns and rifles, I'm not sure which I like more but if they both sound right, then they're great.
This is a weird question but I think games where characters yell satisfactorily when they die are the best ones. People normally don't account for it in sound design, but I do.
btw I'm still begging my sister to play Serious Sam a lot.