The thing in this game that never fails to put a smile on my face are:

Doing things with friends; so many fun and crazy people, I love it
The story: I never ever try to guess of speculate whats gonna happen next so when story expands, I am like all the way.
A good death flare in the face of a big mob of enemies > Flare used to do this but since its nerf, not happening
Totally destroying a huge pack of mobs in a dungeon with a double summoner or summoner + black mage combo
And finally, although has not been been making me happy recently, getting a good piece of gear I have been saving up weeks worth of tomes for

You guys don't know, but my luck with loots is terrible, so much so that I have just flat out given up on any sort of loot that can be considered an upgrade. Like the Void Ark gear by patch 3.1. That also put a smile on my face. No more void ark farming, woo!