Hobby Components Uno Plus

The extra pin headers compared to a standard R3 make wiring up prototypes much easier. I've been very impressed with the build quality for the price, and it's been rock solid in my projects.

The built-in voltage regulator runs much cooler than the standard Uno, which is a nice surprise for longer projects. I also like having the extra I2C connector pins for plugging in sensors without a breadboard.

Swapped to this after my old board died, and the improved power regulation makes it run noticeably cooler during long coding sessions. The extra USB port is a nice touch for powering peripherals without a separate hub.