Some of my games that were under 5€:
Pony Island. Don't let the name fool (foal?) you, this isn't a game for little girls; hard to tell you more without spoiling anything apart that it's mostly a puzzle game.
Plants vs Zombies. Careful, you won't see the time fly by...
DLC Quest, a short but great game that mocks DLCs and brings them to their logical conclusion, horse armor included
Snowball! Imagine your neighbourly park fully snowed over and as a flipper table, perfect for small breaks
There are also several games that are even completely free that are worth more than just a look. Here's two that have always been free (so not old games that have become freeware after several years of commercial sales):
Sunrider: Mask of Arcadius is a mix of VN and pretty challenging turn-based tactics gameplay with mechas and spaceships that will challenge you quite a bit and comes with a high production value.
Pathos is basically NetHack with 16-bit style graphics and some QoL additions and changes. Also available for mobile phones.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454 List as Google Doc: https://docs.google.com/spreadsheets/d/1aW2hXQT1TheElVS7z-F3pP-7nbqdrDqWNTxl6JoJWBY/edit?usp=sharing
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/
Free Pc Games thread: https://gamrconnect.vgchartz.com/thread/248138/free-pc-games/1/