Brain Games
LogicLike
Dualnback.works
JobFlare
Hue Brain Games
Pixelogic - Daily Picross
The Dodo
Wee Puzzles
Uberchord Guitar
Fretello
Guitar Pro 7
Justin Guitar
Fretuoso
Go PlayAlong Tab Player
Moosiko
Guitar Trainer
Brain GamesI've been using Uberchord for a few years by now and it's just amazing. It's all about chords, rhythm and songs. This is no child's game, though, you actually learn how to play. The recognition works for most of my guitars and is borderline crazy, even showing me if I put a finger on the wrong fret. It won't let you just play anything and still pass. They have courses library (they call it learning path) and a pretty large catalog of popular songs. I wish they had solo training, but all in all, highly recommended.
LogicLike - Improve logical thinking through engaging brain games
Fretello - Duolingo for learning how to play guitar
Dualnback.works - Dual N-back is a specific brain training exercise, that's been shown by research - it might improve fluid intelligence.
Guitar Pro 7 - Create, play and share your tabs
JobFlare - Brain games for job seekers
Justin Guitar - Over 750 completely free guitar lessons!