I'll just go through my library and pick out the ones that I don't think are very well-known or might have been missed by anyone who got into gaming more recently.

Demon Truck is a devilishly arcadey game, and at 90% off it is fifty cents so you are legally required to buy it right now. Once you play it for a few minutes, you'll want the BANGER soundtrack too, which was done by Zircon, costs $3, and is worth every penny. Here's a sample on YouTube if Bandcamp doesn't work for you. Game is a 40 megabyte download. What are you waiting for?

Approaching Infinity - What if No Man's Sky was a turn-based roguelike with retro tile-based sprite graphics? If that appeals to you, give it a look. The developer also has a more fantasy-oriented game called The Curse of Yendor.

Devil Daggers is worth trying if you enjoy fiendishly hard FPS games with pixel graphics.

Bots Are Stupid - it's a tight platformer where you control the character by writing a script to control its actions down to the individual frame if necessary. It has a level creator as well. If you've ever seen tool-assisted speedruns (TAS), this game is basically creating a TAS for something like Super Meat Boy.

If you have PCVR, give Ancient Dungeon a look. It's early access, but it already has that particular spark that tends to (and did) hook me, and it does a number of things phenomenally well, such as knife-throwing. In lists of top VR games, however, I rarely see it get a mention.

Distance is a racing game with where your car can jump, do flips, fly, stick to walls or the ceiling, and potentially get cut in half by the road hazards. It's by the same developers and is the successor to the equally fun and completely free Nitronic Rush.

It's not on sale, but at $5, Noitu Love 2: Devolution doesn't need a sale to be well-worth the price.

Lastly, Timespinner is a pixel-art metroidvania with time travel. I thought it was pretty fun.