Prator: My biggest complaint about Far Cry is that it gets ridiculously hard in the later levels of the game, especially when you're fighting massed groups of trigens. As for human enemies, I found that they were often able to spot me through the jungle foliage (and through tent walls) even if I could not clearly see them. I beat the game by using the strategies I learned in S.T.A.L.K.E.R, which basically boil down to "take cover and aim for the head."
There's also the tried-and-tested "mod the AI so it doesn't have Geordie LaForge's visor and hearing that could only result from scattering thousands of WiFi-equipped DSPs all over the islands and plugging the results into HAL 9000."
(Loud percussive radio boombox playing)
Al: They ain't no fish bitin. This sucks.
(Nearby, a beautifully rendered small waterfall, complete with 110dB white noise; a merc practices emptying his magazine at a target five meters away)
Bob: I wouldn' go fishing round heah. There's SHAAAK in the water. You know what they feed the shaaaaak around here?
(Helicopter flies overhead)
(Player triggers "oops, I farted" script by low-crawling through the tall grass around the base of a steep hill a safe distance away)
Al: What's that? Magnetic 210, range 115 meters! Spam him with grenades while I get my M107 from the armory!
Bob: Naw, I reckon I'll call the Worldwide Infiltrator Hotline and then run straight at 'im wit my piece set to rock and roll!
(Helicopter comes back, starts firing rockets and chain gun)
Player [having examined the entity configs out of pure frustration]: Holy crap, they really can see through walls. [debug sight and hearing range] Well, okay, I guess fair is fair. I mean I heard about TriGens later on with wrist mounted rockets who fire at you at point blank range, and I haven't seen -- OH COME ON!