The game that I have played the most is probably Minecraft: Bedrock Edition. I enjoy making redstone contraptions in my redstone testing world (my last project was an 8-bit four function binary calculator) and have also experimented with command blocks. Unfortunately, Minecraft: Bedrock Edition seems to have broken after a recent update (it is completely unplayable), so I've been playing Minecraft: Java Edition mods/datapacks (like deathswap or the gravity mod) with my friends. I've also played Portal 2, Undertale, and Deltarune.
Some other free games that I play sometimes are Banana Shooter, Grapples Galore, and Muck.
Some underrated games on Steam are The Werecleaner and Sheepy: A Short Adventure.