Official and probably rarest: OTFCC Sideswipe and Sunstreaker 3rd party: MMC Knight Morpher Cyclops (Hearts of Steel Shockwave)
G1 Starsaber, Victory Leo, and Dezarus. I take pride in maintaining their nice chrome since I was a kid.
G1 Skywarp drone-buddy mockup/prototype -Generation 1 Seekers Companion Product Mock Up Revealed Transformers News Reviews Movies Comics and Toys Grey Four Star jet -
I don't do MISB or rare collectibles or anything, my collection is for mine and my 5 year old daughters viewing (and occasionally playing) pleasure. Prize/centrepiece will be Toyworlds Devastator in all his huge, absurd glory. Three figures, down, a fourth on the way and once those last two are released I get to see if he'll even fit on my shelf or if he's too tall. (I suspect he'll be too tall so some creative posing will be required.) I honestly can't wait to see my daughter's face when she first see's this guy fully assembled.
Car Robots Brave Max E-hobby diaclone Magnus Binaltech Smokescreen Botcon 2006 box set + Megatron and Waspinator
I have to confess this guy is amazing and I have been seriously tempted several times. He has absolutely no place in my collection but still...SO COOL!!!
I really wish we got an official toyline out of Hearts of Steel. Shockwave is amazing in both modes. He was the first real expensive figure I ever got. My wife gave it to me for my birthday a few years ago. I did manage to pick up the Commander mold but in colours so I have Hearts of Steel Shattered Glass Not Optimus Prime Not as impressive or intimidating
Crown jewel....hard to say...I have so many prized pieces in my collection I don't know which has the highest value to collectors...
In terms of most expensive individual figure, CarRobots Brave Maximus (with add-on red rifles & blue sword) & HK ACGCon Metroplex could be my "Crown Jewels". MP01 & MP04 Optimus are also up there. Anniversary Unicron, G1 Anime Astrotrain, G1 Anime Galvatron, 00 Reissue G1 Megatron, New Year G1 Optimus Prime, Takara Re-Issue god-Ginrai, etc., or even my huge Hard Hero Unicron statue, are all contenders to that illustrious title. If I could get my MP01 box signed by Mr. Cullen, that might become my ULTIMATE "Crown Jewel". Of course, having collected Transformers for 30 years, there are many G1, G2, Beast Wars, and other older figures given to me by my Parents, Brother, Family, & Friends, which I treasure for sentimental reasons and could never part with. This makes choosing a favorite very, very difficult. It's almost like asking which is most awesome, or most wonderful, or most marvelous or fantastic, or which is most amazing, most fun, most cool, or most must-have. I guess I just can't decide...but what a lovely conundrum to live with!
Good men! I have both, and they are definitely right up there, but my personal crown jewel is Beast Wars Neo Black Big Convoy.
A few that stand out to me: WeiJang oversized MP Optimus Prime WeiJang oversized AOE Evasion Mode Optimus Prime reprolabeled Titan Metroplex Titan Devastator (soon to be outfitted with various 3P upgrades) oversized MMC Feral Rex
Diakron Blue Trailbreaker Mail away '86 movie Optimus Prime (complete) Canadian Slag (complete) Reflector (complete)
Easy: MIB unused C-131 Raiden giftset. In fact I'm such a fan of Raiden I also have a set of the six seperately boxed Trainbots, most of which are either MISB or MIB unused.