We've already got a discussion on ground-breaking 00 locos, how about an equivalent thread for N?
To set the ball rolling:
Lone Star D5000 (class 24). Lone Star were just a little too far ahead of their time in 1960, but their two British-outline diesels were pioneering models, despite their rather crude mechanisms.
Minitrix Warship. Though crude by today's standards and had dimensional compromises to fit a continental chassis, it was as good as any British-outline diesel or electric model before the 1980s, With its robust and reliable mechanism it was the workhorse of many a layout in the early years of British N
Peco/Rivarossi Jubilee. Credited with establishing 1:148 scale, it was way ahead of its time in terms of detail and accuracy. A bold step for Peco for commissioning this in the very early days of the scale.
Graham Farish class 47. This loco marked the point where Graham Farish went from a bit player to becoming the flagship British N manufacturer. In a different league to any main-line diesels before that point.
Dapol 45XX. The entry to Dapol into the marketplace forced Farish to raise their game. Though the mechanism leaves something to be desired today, in terms of detail and fidelity it was way ahead of any other steam outline model on the market at the time.
RevolutioN Pendolino. A game-changer in terms of business models, introducing the concept of crowdfunded models to the marketplace.