Games Radar did a list of the most common enemies we have to face over and over again and I have to say it's hard to disagree
1: Suicidal mercenaries
Recent Offender :
Uncharted 3 has this in spades, though the whole series is guilty of it. In one of Uncharted 3’s most intense sections, Nathan Drake has to make his way out of a burning building on the verge of collapse. And with fiery death all around them, the mercs still shoot at Drake from behind (burning) cover. Maybe the big bad of the game only employs gunmen diagnosed with suicidal tendencies.
2: Helicopters
Recent Offender:
50 Cent: Blood on the Sand taught us two things: That the rapper/business mogul is great at killing terrorists, and that he HATES helicopters. Fiddy blows up so many choppers in this game it borders on parody, with multiple boss fights ending in a climatic helicopter shootout. We’d have appreciated it the bosses had instead jumped into a hydrofoil once just to keep things interesting.
3: That same guy you just killed, but with a different hat
Recent Offender: Killer is Dead
The recent Killer Is Dead falls into this trap a lot. There are around seven types of common foes, and they come in a number of colors. Sure, you killed that red, mace-swinging giant 10 times already, but you haven’t killed him when he’s blue and wearing armor, have you?
4: Orcs
Recent Offenders: Warhammer 40k: Space Marines
Warhammer 40K: Space Marine not only has an incredibly obvious name, but it also has a limitless supply of orcs to throw at players. Technically they’re “orks,” but the name change and added space armor aren’t fooling us. The green jerks bleed all the same.
5: Zombies
Recent Offender: <Insert almost any game from the last 5 years here>
For the rest of the list and a more in depth look at the others, go http://www.gamesradar.com/9-enemies-were-tired-killing/