I like all Titleist equipment! For me though, my favourite has to be my irons. Just the confidence standing over the ball(ProV1x) with iron in hand.

Great question Mike...
I love all my Titleist clubs, and was cutom fit for everything other than my Scotty.
I am sure I am not much different than most when I say that each round I have a different favourite. One day it will be the driver, another day my AP1's, the next it will be my Vokey's, and yet another it will be my GoLo Scotty.
Not to worry, the Fairway Metal and the Hybrid take their turn as well :)
Over all, I would have to say that the Scotty Cameron putter is the biggest game improvement club in my bag mostly because I use it on every hole day in and day out. My putting average has dropped from around 38 putts per round down to 33 putts per round. I have had a day when I walked off with 28 putts which was a personal best and it left me with score that was 3.6 strokes below my index :) You have to love those days.
Over all - since I started adding more and more Titleist products to my bag, my game has improved measurably. These days, I am happy that I am still scoring like I did 10 years ago (or slightly better) given that as the years keep creeping up on me, the less distance I get making it more difficult to reach those long 425 yd par fours.
Darius

My favourite club has to be my 980 3 wood.I have not been able to find a newer Titleist 3 wood to replace it. I just have extreme confidence in that club. I do like all of my other clubs the 915 Driver is nice, my 913 hybrid is great, the AP2 irons are great, my new SM6 wedges are the best. My Scotty putter has had issues lately but when doubt creeps into the old headbone it is the old 980 3 wood that provides comfort.

As an aside I talked to Ken, the Titlesist rep for our area, he told me that 3 woods are the clubs that are replaced the least.