puzzler

noun

1. A puzzling situation or problem.

   “And reason cannot answer that question, because it exists outside of reason. It’s a puzzler, right? A real head-scratcher? Which brings us back to me.”

2. A puzzling person.
3. A puzzling person.

   “Near-synonyms: riddler, quizzer, setter”

4. A video game in which the player is presented with (usually abstract) puzzles to solve.

   “With the exception of certain handheld titles […], puzzlers (such as the countless Tetris iterations), and download-only games […], two-dimensional gaming has largely become a lost art, alienating many of us who grew up in a 2D virtual world.”

5. A person who solves puzzles as a hobby.

   “[…] he commits what to a hardened puzzler seems an unforgivable sin when he uses a picture of a two-masted ship followed by HTER for the word BRIGHTER.”

   “Mentally stimulating leisure activities, such as doing crossword puzzles, seem to help keep the brain sharp. […] The puzzlers delayed the onset of accelerated memory loss (a sign of dementia) by an average of 2.54 years.”