[DISCUSSION] What helps you choose milestone platinums?

I've always used a method if you will to milestones, they've to meey a specific criteria:

Fun, must be 100% attainable not just platinum if there's DLC, a specific connection with the game or series and generally its a PS3 version for nostalgic purposes.

I'm closing in on my final Milestone before I call it a day and focus on well life and obviously want to make my last hurrah a memorable one, My question is: what primarily makes you decide your milestones? Fun, difficulty, rarity etc?