The LT-40 is excellent. Personally can't stand the PT-40, though lots of people have had success with them.

A now-overlooked kit is the Golodberg Falcon 56. Maybe they call it the Falcon III or something now. One of the few 40 size trainers I've seen with the semi-symmetrical airfoil that is really suitable both as a primary trainer and an advanced one. It will fly decently on a good 25 or 28 motor, or really tear things up with a light 40.

The Sig Seniorita and Kadet Senior are wonderful 3-channel trainers that will teach you a ton about how to really fly an airplane and not just point a ballistic missile. Build them by the plans, avoid the temptation to stuff in a huge motor, and no ailerons. Absolutely a blast, once you understand the method to the madness. Whatever you do, have a blast!