Little simple things you quite like in games?

This can be anything from small simple details to basic gameplay mechanics... And it can be in any game. It just cannot be a 'feature' or a major part of a game.

I name A LOT of things, honestly... Most of them from The Elder Scrolls series but a new one I recently figured out was in Halo Reach, in the firefight map of the Anniversary pack... What is it? At the beginning both the 2nd and 3rd round in a set, you get an ODST ally and new warthog... Keep the first one alive in the 2nd round then the final round in a set, you can do http://i.imgur.com/JMWFZrO.jpg and I LOVE DOING THAT! And it really just a small simple thing that most players probably don't bother to pay attention to and actually let the allies get killed most likely... (Though hate it how the two allies will die at the beginning of the bonus round).

Untold stories that have nothing to do with a quest but just your imagination as to what it is or what happened, all scattered through TES and Fallout.

Many things I like in a game can go down to "make the game world feel alive", which can good character writing or gameplay mechanics or anything really.

One thing, for example, is that I like to be a stalker in games, sort of Like back in 2000 when I played Deus Ex I would go up to some high spot and watch NPCs/enemies on the other side of the level with binoculars and just watch them walk around and stuff. And I suppose that's kinda a "thing" for me in games, being able to watch NPCs do stuff over great distance. Which makes them feel like they don't depend on me, the player character, to do stuff, and thus more "alive".

Any sort of character or loadout customization in singleplayer wins it for me every time.

I honestly do stuff like this too... Normally when I'm playing on my main in Skyrim, I don't bother fighting myself anymore (Unless I want said thing to die ASAP)... I just get different NPCs/Enemies together and let them go at it while I watch.