I've been playing HL Alyx, and there are just so many fun interactions you can do in this game. Like, you can grab a gasmask or hardhat, put it on, and it'll be functional. Or you can grab a metal plate or barrel, hold it in front of you and use it as a bullet shield. You can grab a bucket, fill it with grenades and carry it with you through basically the entire game. When a headcrab jumps at you, you can grab to intercept it mid-air, and it'll be helpless while you pull out your gun to execute it. Or throw it down a pit, or trap it inside a barrel, or feed it to a barnacle. There's no melee damage, but you can smack enemies with stuff or throw at them them make them flinch and buy a little time. Also grab and throw back grenades. You come across a functional piano at one point, and you could play songs on it with some practice. Bottles have pretty realistic liquid physics in them, but when you put it to your ear and shake, you can also hear it sloshing around. I tried throwing a light switch, and it worked. There's functional markers at the start of the game that you can draw with on any glass surface, not just at the beginning of the game.
There also tons of easter eggs, to the rest of the Half-Life franchise obviously, but there's also a TF2 Scout figurine, a Portal turret grafitti, a Bridges branded package from Death Stranding, and an 0451 reference.