Have You Played? is an endless stream of game recommendations. One a day, every day of the year, perhaps for all time.
I don't have a single favourite FPS and find such conversation boring but if someone asks and I want to test their mettle, I'll tell them it's Far Cry 2. If they say they prefer Far Cry 3, I know they - as a person - are wrong. Far Cry 2 is a game about plans and contingency plans, then desperate makeshift plans when those both go wrong, then finally, after a crucial grenade rolls back down a hill towards you, hoping that your buddy will come pull you out the fire - and that you can cover them. "Far Cry 3 is for babies," I'd probably declare, because I'm like that.
Far Cry 2 is an open-world FPS set in a nondescript African country mid-civil war, where you're out to kill a notorious and elusive arms dealer. Whatever. That doesn't go to plan, and nor will most other things you intend to do.
The interactions of a few simple elements - flammable flora, stealth, a health system requiring DIY first aid in the field (gruesomely resetting broken fingers, cauterising wounds, and wrenching inexplicable lengths of rebar out of arms), disorienting malaria flare-ups, AI patrols, large landscapes, and our dear friend physics - lead to all sorts of mishaps.
A plan to sneakily mortarbomb a target from afar might see you narrowly miss and spark a wildfire blowing back towards you, leap into a jeep to chase them down, crash, swap your pristine long-range weapons for some short-range crud an enemy drops, hidebehind a shack to heal yourself, have your swiped shotgun jam (the animations are splendid) and eventually blow up, then finally nail your target by detonating an IED in their path. It's pretty great.
When everything goes well, you feel godlike.
I usually roll with the bolt-action rifle (I prefer the chaos opportunities its noise provides over the silent tranq gun), flare pistol, and mortar, since you asked. Backup loadout? Silence MP5, grenade launcher, and tranq gun - but it's a little too well-balanced for my liking.
The problems some complain about - malaria, jamming weapons, NPC outposts respawning with silly frequency, and so on - are what make Far Cry 2 so much fun, creating more opportunities for unexpected cockups for you to triumphantly recover from. That's where Far Cry 2 shines.