You simply need to try A Short Hike. I do believe it is a sin to not play it. This is one of those experiences I'll never forget.
I also really liked Jam and the Mystery of the Mysteriously Spooky Mansion (jeez, what a name...). It's a charming whodunnit, where you already know who did it.
You should also try Minit. This is the sort of game that I aspire to make myself, top quality stuff. There's a huge world with secrets and puzzles to solve, all oozing with charm.