I think the sort of speed puzzle games would be pretty cool. Something like Bejeweled Blitz. In those games, they're free to play, have competitive leaderboards with your friends and boosts that cost money. So you can spend some Steem to buy boosts to help you get to the top of the leaderboard, make shitposts with your highscore, and the game owner could use some of their SP to upvote people's posts. Especially the people at the top of the leaderboard. Maybe at the end of the day top 3 spots of the leaderboard get a 100% upvote.