here's a bunch of top quality games on Amazon Underground, better hurry if you want any of em:

these links should all be correct, for the 100% free Amazon Underground versions of the apps. let me know if anything's wrong

• monument valley
• gunbrick
• hitman GO
• lara croft GO
• deus ex GO
• shadow blade
• shadowgun
• monsters ate my birthday cake
• inferno+
• hook (removed from Underground, but available for $1 on Amazon or on Google Play)
• quell
• quell reflect
• quell memento
• the westport independent (removed from Underground)
• puzzle retreat
• type:rider
• almightree
• splice
• dark echo
• punch quest
• badland
• duck tales: remastered (removed from Underground)
• castle of illusion: remastered
• god of light
• all Cut the Rope games + Pudding Monsters
• where's my water
• where's my water 2 (removed from Underground)
• where's my mickey (removed from Underground)
• where's my perry
• toy story: smash it!
• threes
• ghosts of memories
• blown away: secret of the wind
• hitman sniper
• magicka
• goat simulator
• goat simulator: waste of space (removed from Underground)
• goat simulator: goat-z (removed from Underground)
• goat simulator: mmo simulator (removed from Underground)

added from the comments here:

• star wars: KOTOR
• siralim and siralim 2
• games by Halfbrick
• sonic CD and the Sonic dash games
• sorcery and sorcery 2
• knights of pen and paper
• delight games interactive novel collection
• pac man championship DX, along with tournaments and friends

if anyone likes Hidden Object games, there are a bunch from:

• artifex mundi
• big fish
• G5
• Five-BN

you can go here to search for others, make sure the search bar says Underground Apps before you search.

Lara Croft GO is also available. No idea if Hitman GO is gonna get in on it too or not.