well for me it is my Peugeot Prestige for what concerns road bikes because it is with this bike that I started racing back in 1996 and it is currently being upgraded with Dura Ace 7800 components
For mountain bikes, I will stick with my Kona Kilaeua from 1997 which due to its very agressive geometry is real blast to ride and also lightweight
It is followed by my Scapin another great mountain bike with a less agressive geometry but still a very responsive and lightweight frame
With the new road bike projects and the last MTB project that will be build , things might change