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.