An honorable mention is this little guy, the Fruit Bat. It was one of my early designs in KSP and is mostly aesthetic rather than innovative or extraordinarily capable. An all electric atmospheric plane, the fruit bat is not particularly fast and is not designed for orbit. It is fun to fly though, and performs like a solid little jet. It was designed to familiarize myself with the all electric propulsion systems in KSP and to proof the onboard electric generation systems for long range flight. 
The Fruit Bat is reliable and fun to fly, plus it looks like something straight out of a sci-fi anime, and that was kind of what I was going for. 

​-NR