The section of the manuals that is dedicated to games contains information about games and toy-like programs. These are distinct from utilities listed in the first section and administrational tools that live in the 8th section in that they are not considered important for the use and maintenance of the system. Hence the separate section for them.
Most of these "games" would be command line, character-based, applications.
You may list the manuals in this section on Linux using
man -s 6 --regex -k '.*'
That is, "show the title of all manuals in section 6".
The following is explicitly about "games" on OpenBSD, although some of these games and toy-like utilities may also be packaged for Linux.
ls on the appropriate directory:
$ ls /usr/share/man/man6 adventure.6 bcd.6 factor.6 hangman.6 morse.6 quiz.6 tetris.6 arithmetic.6 boggle.6 fish.6 hunt.6 number.6 rain.6 trek.6 atc.6 bs.6 fortune.6 huntd.6 phantasia.6 random.6 worm.6 backgammon.6 caesar.6 gomoku.6 intro.6 pig.6 robots.6 worms.6 banner.6 canfield.6 grdc.6 mille.6 pom.6 sail.6 wump.6 battlestar.6 cribbage.6 hack.6 monop.6 ppt.6 snake.6
It's interesting to note that some of these BSD "games" could actually be considered useful, such as
factor which factors a number into prime factors, and
primes which generates prime numbers. Also
banner is used on some systems to generate (very) basic banners.
number tool could also be considered useful under some circumstances:
$ /usr/games/number 23 twenty-three.