Please advise

Hey Veeky Forums,
which system would you recommend with FUN (I know, I know) firefights? Would be looking for modern-ultramodern setting.

Maybe D20 (I've heard good things), I started making my own game for just this reason,

GURPS

Well, how do you define fun?

I mean, Dark Heresy firefights are always a delight.

Tactical shooting is actually my idea of Fun. It's really fucking fun.

Though OP didn't specify what type of fun. He may not like that type of fun, and instead prefer other types of fun. Like being a shooty guy in Fung Shui.

steal reaction fire from original xcom pls

Eh... Not fond of d20. Played it too much back in the day and d20 wasn't a real good system for handling firearms in general IMO.
I am familiar with GURPS, but isn't it little too overcomplicated at handling firearms? I mean, all the range penalties and stuff. Maybe I need to re-read the rules again, but I hated it for modern.
I guess a mix of realism and fun must be there. Enough realism to warrant individual weapons, but enough fun not to have roll to clean your rifle after every encounter.
I also like Dark Heresy, but somehow unsure if it will work with modern day weapons.

The 40k rpgs' firefights are fun in large areas. Don't ever put the group at one end of a corridor and the bad guys at the other. That's just a roll of.
Also put a 1min timer on each player so that that one faggot doesn't take 10 literall minutes to decide which guy to shoot when everyone includeing him knows exactly whom he is going to shoot! Jesus fucking Chris just roll allready! ARGH!

What do you mean by 'large areas'?
I use square/hex grid, so what distances are we talking about here?
Would it not work in CQC scenarios?
How does cover/concealment work in 40K?

Dark Heresy needs some tweaks. For suppresion mostly as it affects people way to much after geting out of immediate danger.
I'd give a character that has been shot at a penalty to his BS for one round (1 per bullet fired at him, more for scary stuff like Artillery, grenades, and Sniper fire). To a maximum of 20 and after that he has to beat a WP-1 per point beyond 20 test or suffer a more severe penalty (stress, fatigue, losing an action, has to stay in cover etc. Make a table).

The guns the system is made for are generic enough. The Autogun is basicly all Assault rifles for example. And in a modern setting there'd be much less Armor so you don't have to worry about invincible PCs.