Topic like this is 100% subjective to what stirs emotions in the individual. When things happen to people you have begun to care about for what ever reasons then you get your own emotional moments. Many of those don't move the needle for me personally. Stuff that elicited emotions of though for me involve some of my favorite fighters.
Shogun beating Arona was very significant to me when it happened.
Shogun beating Rogerio was also, even though it was several months after the fight happened before I got to watch it and I knew the results.
Hedno KOing Wanderlei in Vegas was huge.
Machida getting the bad decision over Shogun killed me, then the redemption KO in the rematch was elation.
BJ when he gets the sad eyes after a tough loss.
Fedor against Bigfoot was worse then the Werdum loss, the first time he really lost the fight aspect of an MMA match like that.
Cain defeating Lesnar was big for a lot of good reasons.
The Shogun vs Hendo draw was an emotional highpoint.
Other things can stir emotions as well like fan made media. I remember the first time I watched 'A Matter of Pride' by boondocks. Serious goosebumps. The fan made trailer for the SF HW Grand Prix did the same thing. There are a ton of instances that are awesome. The incorporation of well crafted art into this crazy sport is a beautiful thing sometimes.
I like MMA less because of this forum