- Enemies that incessantly dodge and/or heal.
- Lightning Bruiser enemies (hit hard, move fast, have good health and/or defenses).
- And the biggest one, instant kill attacks. Never fails to enrage me, regardless of prior frustration levels.
There's probably more, but I can't think of them at the moment.
No wait, I forgot one: Stunlocking. When I'm not raging because I've been walking along nothing for half an hour, I'm raging because I have been able to do literally absolutely nothing for the best two minutes while in the middle of a fight.
I was once playing an MMORPG, and when I finally got to the boss, suddenly the game would start lagging and nothing would work. Then, just when I'm about to attack, the game would freeze for a few seconds.
Then suddenly, my character drops dead and everything flows smoothly as the game tells me I should revive.
Worst part is when I choose to revive and the game lags again.
I just have a new one: Not being given sufficient advance notice of services are being shut down. Totally hated it when Nintendo announced the DS Wi-Fi shutdown: I was playing BW and was in the middle of doing a quite cumbersome level-grinding against Elesa, and my original plan was to battle the E4 in May, and finish the regional Pokedex in July. I swear, this was the closest I've been to send an abusive tweet full of expletives to Nintendo/Iwata-san's twitter account(s). (Well, that was a bit of an exaggeration, but yes, it makes me wonder why GameSpy didn't tell us this much earlier.) And for goodness sake, if a subcontractor's causing such problem, then tell me so!
I find it really boring when I have to look everywhere for something and I am not given any clues on where to find it. An example to this would be if you have to find a particular item in a town, but you have no idea where it is and nobody in the area will hint at where to find it. I find this even worse if you need to speak to characters in a particular order and/or the item is hidden in a hard to find spot. This is not fun for me at all. At least I don't have these moments very often...
I also don't like it when there isn't an option to skip cutscenes in a story-heavy game. I really enjoy Kingdom Hearts and Final Fantasy X, but I get a little impatient sitting for minutes just so I can try fighting a boss again. I already know what happens, so let me just get to the battle!
One more thing that I really dislike is the lack of a save feature. Believe me, I enjoy a good challenge here and there, but not if it's from the fact that I have to start the entire game over if I lose too many times. If there is a password system or if there are cheat codes that let me skip levels, I can possibly forgive this to some degree. Otherwise, I find it a chore to repeat the entire game multiple times just so I can get back to the last level I was at.
Especially when something you're looking for (either an item or an enemy) is random. The game seems to know what you want, and gives you something else. Bonus points if what you get is the last thing you want to see (especially if the thing in question is an enemy).
DLC. I've paid good money for a game and it isn't even complete - HOW is this fair or right?? I want ALL the characters/accessories/extra missions in the programming from the start. I don't mind unlocking these things through gameplay, i do mind unlocking through paying more.
Games that assume/expect everyone has internet connected to the console. I've missed out on achievements, exclusive content and playing against others this way. Updates/patches are too reliant on this, but there's not really another way to rectify that. Also the problem with limited time frames (Mario Kart wii and Pokemon GTS for example) means that even if we do get that internet connection, it is useless for older technology.
Residual damage. Sure, it's OK if it's limited to, say, a toxic pool or lava, but if you take damage just from being outside of whatever safe zones are available like in Metroid Prime 2: Echoes' Dark Aether then that's just evil. It also dosen't help that until you get the Dark Suit you lose energy faster than the safe zones can replenish it and some safe zones have to be shot to actually protect you.
RNG. Usually because I get screwed over, from 70% crits not working to the enemy hitting with a 20% hit rate (lost Kjelle in Awakening this way once; for example, best example I can think of, I thought I could kill the boss, but his two-hit attack hit on both 20% chance, technically making it a mere 10% chance to die, RNG usually loves to screw with me.
Also, crappy graphics on certain games. Take Pokemon Conquest for example, a really fun, surprisingly deep and addictive gameplay is set back by me for it's shitty in-battle models for attacks and such.
Evil quest bosses that are tougher than a regular boss. For example, there is a quest boss that pulls a pretty F***ING annoying trick on you from Etrian Oddysey Untold: The Millenium Girl: the Golem. (COMMENCE RANT!!!) What is this trick, you ask? Well, if you do mannge to reduce the behemoth to 0 it F***ING RIVIVES WITH HALF OF IT'S HEALTH (i.e. 3000 HP) AND THEN PROCEEDS TO REGENERATE MORE HEALTH THEN YOU CAN TAKE AWAY EACH TURN for four turns. It does not help that it takes FOREVER to reduse it's health to 0 in the first place, or that it's attaks either have a splash effect (meaning they hit party members on either side of the target as well) or are multi-hit moves that both do about 45 damage per hit when it's attack is redused (which is a lot at this point in the game,) or that by the time you get it to 0 the first time your Alcamist and/or Medic is probably either low or out of TP, which means you either have to go without Elemental attacks/healing skills or use them sparingly.
When you go through a level just to find out you got to back track just because you missed something not very obvious and you need it to finish >.< Also timed missions that barely just give you enough time to finish, screw up once and you might as well restart. But the one thing I hate most is micro-transactions where you can just buy stuff and win the game by paying, games that do that need to die in a fire.
When character bosses (I.E. Bosses against a character in the story, rather than a monster or something more common.), have the same moves or skills as you (For instance: if the game has a Limit Break system, the character bosses will also have Limit Breaks.), but they don't need to do complicated inputs or wait for certain requirements (Basic making them able to pull out super attacks out of nowhere.)
As much as I like the Tales series, this is a major problem, as later bosses is most games will often use Mystic Artes without needing to be in Overlimit, which is a requirement for you to use them, as well as bosses having infinite TP and no Max Combo limit.