Excellent topic for a thread! For me, the Marutaka B25, but only because of the nacelles. Planking and then fitting retracts/doors into them. To top things off I had some resin not cure on the wing glassing so had to strip it all off. That's how it sits now. The rest of the kit was quite simple. I actually enjoy the Marutaka kits, I just don't like planking on such a small diameter. I later bought their Stuka kit which has a fibreglass cowl, beautiful kit. I also recently bought their .60 size Zero (always wanted a Zero). Both are still NIB, waiting for other projects to be completed.