EDIT: Seems dynamic music is back in style in some very recent games, many of which I haven't really played yet. Good. 
For me, it's dynamic music, the kind that some games had that adjusted moment by moment to what was happening in the game.
The best-known example of this in the 90s game TIE Fighter, where the moment more enemy (or allied) ships showed up the music would have a little additional flourish to acknowledge the shift in battle. There were pre-battle tension tracks, battle music, complications of battle, grandiose flourishes for the arrival of enemy or even allied capital ships, and victory and failure music all ready to flow into the next seconds of the game.
A lesser-known but still excellent example of this was in Ultima Underworld and its sequel, where drawing a weapon had its own special "preparing for battle" tension music, getting attacked had a jump-out-of-your-skin joltingly sudden musical start that actually scared me as a kid when I got ambushed, music for battles going well, going poorly, victory and defeat.
I wish more games did those sort of second by second musical changes, but they've sort of fallen out of fashion for the most part. 
Inventory Tetris. Whenever a game has the player carry stuff in hammerspace it’s almost always done by using a weight system like how Bethesda does it. I want resident evil style inventory where items can take up multiple space slots.
Please play Backpack Battles. Totally awesome if you love trying to place your items optimally.
Some indie im sims also have it. Gloomwood has it, I think. Blood West has it as well.
There is also a mod for Project Zomboid that turns inventory management to be tetris instead of weight based, and integrates gear mods as well.
Indie games are just better.
I made a comment about this elsewhere in the thread, but let me repeat myself here. Pathologic 2, Dredge, and Subnautica all have this. And they're all spectacular games well worth playing. If you haven't tried them, I would suggest it. For Dredge though, don't buy the DLCs, they are not worth the money.