In my opinion, they aren't too annoying. Providing they aren't throwing Plasma Grenades at you in a group they can be easily taken down. At their worst though, I'd have to say it's in mainly Halo 1. Towards the end of the game you found Special Ops Grunts and Elites. These Grunts take a lot of abuse and tend to be very trigger happy with Fuel Rod Guns and Plasma Grenades.
I don't know if they've already been mentioned, but the bosses in the recent Mortal Kombat made me scream my god damn head off. They were so fucking cheap. They'd do mega power moves and it was next to impossible to knock one over, or to even interrupt on of their attacks.
I've heard MK had a good story but I just couldn't finish it out of pure anger towards the stupidly cheap boss fights.
The little prickly things in Zelda Wind Waker. All they do is stick to you and slow you down, the more on you, the slower you move. What really made them annoying was that in order to get them off from you, you had to stop and do a spin attack, which requires waiting a second or two for the charge Link to ready the spin attack. If that's not bad enough, there is no guarantee the spin attack will destroy them, most of the time the spin attack just throws them off you and they come right back to you.
Another one that is a contender in my book against those prickly things in Wind Waker.
In Star Ocean 3, there are two enemy types that have continuous streams of attacks which send you flying in the air, regardless of if you have the "no guard" skill equipped and maxxed out (it's a skill that leaves you unphased by attacks that make you stagger or go airborne). The two enemy types, Vendini with carbine rifles and spider robots, have incredible "no guard" skills, so staggering them or sending them airborne is out of the question. Get enough of either or both in the same combat, and your stuck watching your hero fly up into the air, fall to the ground, up into the air, fall to the ground, ad-nauseam. What makes this so annoying is the AI's natural reaction to these particular enemy types are to run around avoiding their blasts/missiles, so you wind up having to spend a couple hours teaching each of them to just pummel those enemy types to get them dead asap. When I say teaching each of them, I mean controlling the characters for around 10 to 20 minutes in that specific situation, doing exactly what you want them to do (the AI learns from how you control any given character). And then you gotta pray that the AI doesn't wind up getting pummeled by those enemy types too much, because it will learn to run like hell all over again.
Oh my god! I just remembered a bunch of frustrating foes that have yet to be posted up here. Suffice it to say though, I fucking hate ALL OF THEM!
The Three Assholes of Viewtiful Joe
Yep, that's right! These four foes are just downright plain fucking frustrating and even to the point making you go mental. Let's go!
This guy would be the third boss encounter in the game. His moves mirror your moves but with his own words. His worst move though, the mutherfucking "Henshin a bye-bye!". If you so much as let this bastard out of your sight when you fight him, be on the lookout for this attack. He essentially makes copies of himself and each one hones in on you. If enough get you you are going to die very quickly. Very hard to dodge too. He's even worse I reckon when you face the "Fantastic Four" later on. This guy will SPAM THE SHIT out of you with that move.
This guy is hands down quite possibly THE toughest boss in the game if not the second toughest (he easily rivals the final boss). Epic fight overall with an awesome boss theme. It still doesn't change the fact though that he is FRUSTRATING to the core. Fire Leo is the definition of a boss who not only looks tough but actually IS tough. He's extremely fast with his moveset. Asides from running around the field shooting fireballs at you and attempting to run you down. He also loves to use his signature move where he spins in a tornado. You have to dodge his swipes five times when this occurs and you only get a single warning. This is probably one of the few bosses in gaming history which no one has beaten on their first playthrough. Fire Leo will drive you FUCKING MENTAL.
King Blue can talk the talk and walk the walk. Unlike the other bosses, he never is stunned in which you can beat him up whilst he can't hurt you. Oh god no, this guy LOVES to spam you with lightning and missiles and has a large space cruiser that backs him up. You on the other hand are using the Six Majin, Viewtiful's version of Megazord. Timing and dodging are key to winning this battle but by god King Blue will hand your ass on a silver plate. I hate him so much. Oh and don't even get me started on how much health this a-hole has!
The giant snowman in one of the later snow levels is just as bad if not worse. Either way, your immediate priority after the fact is to get your hat back as soon as possible, preferably without getting hit (Mario takes greater damage from enemy attacks/falls/other hazards without his hat on, for those who don't know; the status can also transfer to other levels if you forget to reclaim your hat). I think the vulture in one of the desert levels is also capable of stealing your hat if I remember correctly (been a while since I last played).
A lot of KOTOR could prove to be difficult, but this guy was the absolute bane of my existence. I tried facing him on every planet thinking maybe this next one would be the one that I can beat him on. Every time he blasted my face clean off of my face. I finally beat him on Manaan. You fight him in a narrow hallway and I lined every last inch of that hallway with mines ahead of time.
I don't have a picture of the little pricks, but anyone who's played Halo 3 knows those MOTHERFUCKING Ranged Forms. They immediately force you to cover, pound you with spikes whenever you come out for a second, and the way the game works is that it puts you out of zoom mode when you get hit, so you can't even line up a shot to their exposed section, which is conveniently only exposed when they're shooting at you.Damn these douches. And if you get close enough to be effective, they turn into a stalker form and run away. Damn them to HELL. Spec Ops soldiers from 007 Nightfire. You never know what hit you, all of a sudden, dead. Satchel charges are pretty damn annoying, too. There's always one you missed.