Oh, god. I am a huge weapon-nut when it comes to games. I love how Tripwire gets so many of their guns so perfectly responsive and complete in their animations and behaviours. They've started a YouTube series dedicated to displaying guns from Red Orchestra in real life. That's what I like to see. Developers going the extra mile and doing something different.
I like Crossbows, in general, from the resistance crossbow to the one in Dead Trigger. I love 'em. The only one I haven't been fussed on is the one in Timesplitters 2. Pretty meh.
"Headsprouter, did you just say you didn't like something Timesplitters related?!?"
Yes, yes I did. I'm a crazy fan, but I'm not delusional.
To the OP, yes the flare guns are indeed an awesome part of that game! They feel so realistic and the projectile behaviour is massive fun, but I'm a big fan of the dual machine guns. Feels like a mid-range chainsaw, mows down the competition! Also the double-barrel (I love double-barrel shotguns in general, too...) and the soviet rifle. They just feel awesome to use. Cool reloads, too. I alwasy thought it was hilarious to see characters without thumbs insert two shells into the weapon, like the Dinosaur, Badass Cyborg and...huh. Headsprouter.
The laser rifle from Fallout 3/New Vegas, also, especially the AER14 prototype. Green lasers are my favourite lasers.
And Thornblade from Oblivion. Shame about the enchantment, but that is a damn cool sword.