Quest timers
Forced companions
Forced companion monologues, dialogues, conversation, etc.
Losing companions for "story purposes"
"hard locked doors" that you need story items to advance through
Encumbrance
False choices where it seems like you can choose one thing, but railroads you regardless (better than nothing)
Crafting items and armor that are always better than the stuff you find just lying around
Forced losing to enemies in cut scenes
Having different walking speed than an NPC you are following
Plot essential immortal NPCs that you can't kill
Arbitrary item equip restrictions (class, alignment, etc.)
Mandatory quests that force you to use playstyles you haven't built your character for
Unused party members having no way to catch up with the main party with levels/xp
Blindness
Long stretches of difficult gameplay with no opportunity to save in between
Useless skills (or severe underutilized in the game design)
Factions that have no memory of you murdering all of their buddies as long as you wait a bit
Games that cheat, or artificially break the ruleset in obvious ways - depends, might be good if it helps the AI and makes the game pleasantly challenging
Games that encourage prebuffing before encounters - may be positive, means the encounters are tough; but also means you have to game the system a bit too much
Permanent loss of companions (Battle Brothers, etc.) - as permadeath
Stats or information being buried 3 or 4 levels deep in the UI
Boss fights that introduce completely new mechanics instead of being a "final exam"
Rewarding or punishing the player for playing a certain way (bonus XP for stealth kills, etc.)