I was thinking about some of the small luck based things in pokemon, such as that lady that draws random numbers and if one matches your pokemon's ID you get a master ball...
Anyway I thought there could be a monthly/weekly lottery of some kind that people could participate in to get a chance to win a prize, such as a rare pokemon, or maybe an item.
They could also be leaderboard based contests. Whoever caught the most pokemon in a certain amount of time, or whoever completed some kind of mini-game fast enough...
Then whenever an event ends, there will be a notification that says who won and what they got. that would also be an opportunity to encourage others to participate in the next one.
