1.Having to constantly identify/repair/recharge items: or in general any activity that makes you stop using items and disengage from combat loop in general.

2.Time limits on anything: it just adds stress.

3.Unique quest mechanics not used elsewhere in the game and general "unique" rewards that don't exist anywhere else(such as giving extra skill points from an item).

4.Potion-based combat: basically any game where player needs consumables to play instead of automatic regen: this results in frequent trips back to stock up on potions/scrolls/consumables to resume combat.

5.Mandatory storyline quests: having to complete the same quests again dozens times on different characters. It looks cool in theory, but in practice its just a chore to repeat everything again. Especially bad when quests have cinematics, long speeches/dialogs and fetch tasks designed to waste time.

6.Anti-grinding based on time-spent: basically allowing 2-3 gameplay hours per day that gives exp. Daily quests, daily events,etc.

7.Balance that favors seldom used melee skills and nerfs anything ranged: crippling majority of skills(ranged) for balance reasons. In general shifting balance towards primitive non-magical hack-and-slash gameplay that depends only on item attributes vs skill/combo/tactics gameplay.

8.Having to constantly deal with limited inventory space and throw away items(unless you pay for expanded inventory slots or bags of holding equivalent)

9.Losing levels by dying and death penalties in multiplayer in general, including loss of equipment/currency on death. In general permanent losses from dying in a game not designed to be hardcore.

10.Vendors that charge huge sums for mundane items/consumables or anything labeled as "gold sink"(mandatory or essential purchases with high-cost in currency).

11.Steep experience curves, where new levels demand more than x1.2/x1.25 of previous levels experience(from level X to X+1).

12.Lack of instant long-range transportation between major locations/maps, such as portals to X. Having to waste time on traveling/transport in general.

13.Gameplay that is dependent on items you have and their attributes, and in general games where most of time is dedicated to item farming to get the desired(or even mandatory) gear.

14.Absurd time-investment for getting new levels, such as "Eve Online leveling system".

15.Cinematics: I don't want to see it more than once per lifetime.

16.Random damage: you could deal 10 damage or 180 damage, but you have to prepare for both. Its more annoying when the gap between min-max is large.

17.UberSkills/UberSpells with a large cooldown or huge mana/energy cost built as counterbalance to their power: they feel very limited and situational, instead of mid-range skills that provide most of firepower without cost/cooldown consideration.

18.Item-only skills(charges/consumable) and skills requiring items/stats unrelated to skill performance.

19.Arbitrary limits on currency carried, stacks of consumables size max, inability to stack identical items such as potions,etc.

20.Class-specific items and item requirements in general: having to met certain requirement such as having stats allocated towards the possibility of wearing certain items.

21.Screen shaking/Screen flashing/ Rapid lightning or perspective changing.

22.Indestructible barriers that are actually small fences/walls that realistically shouldn't stop anything and often prevent viewing all of level content.

23. Arbitrary level limits on entering dungeons/maps/levels.

24.Having to have a party to enter instance/dungeon/map/level.

25.Recolored enemies/objects and generally reusing terrain.

26.Geometrically perfect flat terrain with geometric bounds/borders/barrier objects.

27.Having to open doors/locks to advance in a dungeon/map, often opening hundreds of them in a hour.

28.Pointless tactical obstacles that only affect the player.

29.Traps/Monsters that deal damage as percentage of player health or otherwise negating health bonuses/buffs.

As a general rule any mechanic or gameplay element that reduces immersion: having to deal with non-combat game elements during combat, pointless repeated quest/travel time, artificial handicaps, unfair game limits and limited viable options, generally anything that feels like work and lacks choice from the player side.