Right now I think 145 is probably the best division, full of elite talent. Aldo, Mendes, Edgar, Swanson, Poirier, McGreggor. Lots of fun match ups. 185 is pretty awesome too. What about you UG? 
I agree 100% also 205 is usually pretty sweet 
145 is imo the most exciting. Dont care that much about HW or MW although there are few fighters at MW that I really like
I feel like ever since the WEC was merged with the ufc the ftw and ltw devisions are consistently stacked with killers putting on interesting fights
WW
125 or 205. It might be a tie
I like watching them all. But I like WW is the funnest division. You got stacked division of fighters with personality and had a respectable champ.
IAmNotImpressedbyYourStocktonSlap - 125 or 205. It might be a tie125 is severely underloved for sure
205 has always been my favorite for the most part. Most of my favorite fighters come from that weight class.
Heavyweight during Pride's run could have held second, now Im not so sure about todays heavyweight division. Probably still give it second because of fighters like Cain and Overeem who go out there to maul the other guy.
170 as a whole has a lot of great match ups, but has been plagued by groups of lay n prayers & jab n joggers, which dilutes things a bit for me.
At one time I would have said 185 is one of the worst, but it's coming back around now
125 is least favorite (after 135 women).