2012-01-17 (updated 2012-03-08)
These need tag names of some sort.

1) Putting weapons disarmed from enemies directly into use (instead of having to pick them up and select as active weapon).
... examples: TimeShift

2) Player being able to permanently lose certain items without item durability being involved or the player destroying (or "misplacing") them by themselves.
... examples: UnEpic (certain enemies transform player's wielded weapon into a toy hammer permanently, player being disarmed at a spot where the weapon falls somewhere from where it can't be recovered from, and possibly others)

3) Weapons, attacks, or other actions that require target lock before they can be used at all. Although common with guided weapons, this may be required for non-guided weapons as well.
... examples: quite a few games with guided rockets/missiles

4) Randomized level/mission/objective elements, such as locations of objectives/items/characters.
... examples: Revenge of the Titans (enemies randomize from which entrance they come, especially notable with the (mini)bosses), Dead Block (randomizes where the items you need to find are hidden)
= random locations (need something else for randomized enemy sources)

5) Player gets early review/warning of future challenges. Such as the next block in Tetris, the contents of the next wave of enemies, and so forth.
... examples: Sanctum (player can see the contents of the next 5 waves if they so wish)

6) Player can hasten certain challenges. Such as triggering the next wave of enemies prematurely while they're still fending off the previous one.
... examples: System Protocol One and quite a few other tower defense games.

7) Landfill devices - anything that produces extra terrain rather than moving it.
... examples: artillery games (Worms, Scorched Earth, etc.), Mine Bombers, and so forth.

8) Portable environmental objects.
... examples: Blocks that Matter, Trine 1 & 2, etc.

9) Player can carry only a very small amount of ammunition. Limited capacity often works separately of this, where even if you can carry 2 weapons, you still have 10 or more clips for your assault rifle, 500+ ammo for machineguns, 10+ rockets, etc. This would be for cases when you can only have say 3 clips for handgun, 2 clips for assault rifle, 1-3 rocktes, 1-3 grenades, etc. Somewhat like realistic carry limits...
... examples: many but not all survival horror games, hunting sims, milsim, and other simulation games

10) Artificial item limits. Such as limiting how many healing items you can carry even though they reside in your inventory.
... examples: Dark Messiah (can carry only 20 healing items and 20 mana potions, they take inventory slot but you can only have one stack)

11) NPC generation. Like map and item generation, NPCs are generated via some form of randomization. (note: NPC generators is already in use for objects in game world that generate/spawn NPCs)
... examples: Diablo 2, Hellgate, and many games influenced by Diablo [2], and maybe Spore, too ?

12) Natural dialog - It's extremely common for dialogs to be in form of an interrogation regardless who you're talking to or what your relationship to them is, existing only as short questions that the other person oddly willingly answers in great detail. Should one or both types of dialog be tagged? Natural form of dialog is rarer because it often "punishes" players for exploring the choices they have in them without heed to how the other reacts to the overall conversation.
... no examples for this, can't remember any with natural-ish dialogs. Kingdoms of Amalur may have them, though I didn't play the demo very far beyond the tutorial to confirm this. Some instances of sentence based dialog may qualify, though it may be just longer version of keyword dialog and therefore not synonymous with natural dialog.

13) Windows and similar used as entrances. It's extremely common that the player is limited to pre-designated routes for access, such as single door, window, an opening in partially destroyed building, etc. With anything else either indestructible or unopenable even when it doesn't make the slightest sense. Windows in older games were commonly only textures on the building walls, doors being paintings of doors on the walls, and so forth. They could not be used no matter what. There's however few games where these are all treated more or less realistically. Some games only go half-way and only preset cases offer the variety of choice.
... examples: Project Zomboid was recently updated to offer greater variety of choice which reminded me of this, X-Com strategy games environmental/level destructibility at such a level you could create doorways where you wanted, destructible world implies this, non-linear level design implies this as well but is not reliable indicator of it.
.. all this requires is that the potential routes are more than just wall textures (opening or smashing a window shouldn't be that difficult, especially from inside). However, it should be noted that this is not simply about windows being used as entrances, but rather used as entrances besides everything else. So if a building has only an entrance via a window, it's not really part of this since that's the only route.

14) Search within something. In some games player is required to either just hold use key near searchable objects until search is finished or somehow contribute to the search via almost QTE like activity. The most obvious kind is where the player must manually search through piles of objects, but that is probably not in any games yet though Amnesia and other games by Frictional come close.
... examples: I Shall Remain, Dead Block (interactive kind), some modern stealth games probably have this, as well as some tactical shooters might have this, etc.

15) Loading screens or similar include status on loading of something in-mythos or something completely made up. In the former case it's a point towards immersion, in the latter it is humor. Vehicle boot/warm-up sequence, humorous way to say what is being loaded (e.g. "rousing goblins" instead of "loading npcs"), or completely made up immersion related stuff.
... examples: SPAZ (has mostly humorous things in it related to the game), pretty sure there was at least one game where the loading was disguised as mech booting sequence (Steel Battalion, maybe?)
= loading nonsense, immersive load

16) Diverging upgrade paths - ability, structure, etc. upgrades that prevent certain other upgrades from being taken, or simply advance that something in "rank" manner towards specific goal. For example, a basic cannon could be upgraded to multibarrel autocannon or large bore supercannon. A basic flame spell could be upgraded to fireball or gout of fire ("burning hands" in d&d terms). This sometimes makes sense and othertimes not.
... examples: many tower defense games allow diverging tower upgrades, certain RPGs use this as a form of specialization via abilities rather than sub-classing (say 8 basic spells per class which each have 2 or more specialized forms; skill trees where selecting one branch locks out the others).

I'll leave this short this time since the longer (30+) idea threads tend to get confusing.
Edit: Apparently I'm adding more as I can think of them. Still better than adding new threads that seem to be ignored by others, so I'll go with this for now.