Depends on the machine, of course, but some of mine are shown below and they are all on my web page. What are some of your favorite games?
Pinball Wizard - HP67 and HP41
Yahtzee - HP41 (partial to it because I wrote it) :-)
Skunk - HP41 (again, I wrote it)
High Rollers - HP41
Dungeon of Doom - HP41
Wickes' synthetic Hangman - HP41
Synthetic display Star Trek - HP41
which is your favorite? Mine is probably still the Pinball Wizard games.