SdKfz 9 Famo currently building a superdetailed museum piece
PzKpfw III
PzKpfw IV ausf J
In all their variants, so long as it's Deutches Afrika Korps.

Oh how the palms sway in the warm breeze of the Sahara..............

Well, what a popular quetion you asked here eh?

Here goes
1) Pzkpfw IV (Italeri)
2) Stug III (Some resin and white metal kit I picked up at Euro Militare in 1988)
3a) Skdfz 250 (have enjoyed making and scratch building 12 different models Including the 252 and 253 all based on Tamiya)
3b) SdKfz 251(have built 9 variations all Tamiya)
4a) Cheiftain (Tamiya)
4b) Challenger (tamiya)
4c) Warrior (Accurate Armour, the most expensive kit I've ever bought !!!!!!)
5) Sdkfz 222 (have scratch built the 247 using the same chassis)

So those are my top 5 (with sneaky a, b and c here and there).

Mainly Tamiya and Italeri kits, I've only built 1 ESCI kit of the SdKfz 10 and small howitzer, no dragon, academy or hobbycraft kits as yet. Don't know why though, I seen some pretty good write ups on these kits.

I read through the entire thread and found it quite interesting. On ewill never find the best kit in the world information as everybody´s fav kit complies to their personal taste in era or nation.
My number 1 kit is Italeris Big foot. Probably written off by everybody who has ever made it but I get the most pleasure from this kit. I think Im going to pursue more lorry type vehicles in future.
#2 Tamiyas M4
#3 Italeri´s Crusader II
Other kits that could slide into this top 3 depending on my mood are Tamiya JS3, Italeri opel maultier and Tamiya willys jeep

There is some good news for Matilda II fans! Tiger Model Designs is coming out with an update set for the North Africa version probably before the end of the year and then they are coming out with a BEF version sometime next year. According to Joe from TMD, the update will have a new upper hull, turret, PE, and other misc. bits. Coupled with a set of Friulmodel tracks this update set should help you make a great model out of the old Tamiya kit.

Everytime I see this post reappear, I figure half a dozen folks like me think up new entries. So, here goes:
DML M-26 Pershing (fantastic kit)
Tamiya M-8 Greyhound (looks great)
Academy M-18 Hellcat (put a brass barrel on her and she is ready to go)
DJ