copy-pasting what I posted on !pcgaming for some that are $5 or less:

A few super cheap, not-new games I've played that aren't on the main promo banner:

• Aragami - $3 - Pretty challenging stealth game. The sequel is also on sale, but I hear it's more action-oriented, less stealth-oriented than the original.
• Anomaly: Warzone Earth - $2 - Strategy game.
• Bastion - $3 - Same developer that made Hades.
• Mount & Blade: Warband - $5 - Sid Meier's Pirates, but with horses. (This is not the newest game, Bannerlord)
• Sid Meier's Pirates - $2.50 - Mount & Blade, but with ships.
• X3: Reunion - $2 - Sid Meier's Mount & Blade, but in spaaaaaaace. (I've only played the sequel, X4. But this one looks kind of similar, and is two dollars.)
• Tom Clancy's Rainbow Six - $2.50 - Tactical FPS. Been a while since I've played it. Was definitely cool when it came out.
• Tom Clancy's Ghost Recon - $3 - Ditto. This one probably holds up better.
• Tom Clancy's Splinter Cell - $2.50 - Who do you think would win in a fight, Tom Clancy or Sid Meier? I think Sid Meier.
• BlazBlue: Calamity Trigger - $1.50 - Fighting game. Combos are not as timing-sensitive as games like Street Fighter or Tekken.
• Rayman 2 - $1.50 - 3D platformer.