One of the biggest advantages to the Arduino platform is that it's entirely open, both in hardware and software design. This means that if you find the traditional Arduinos - the Uno, Mega and Leonardo - unsuitable for a given task, you're free to redesign them according to your whims without sacrificing compatibility with the Arduino IDE and its wealth of code samples and libraries. The latest to take advantage of this fact is Rayshobby.net, a US-based hobbyist electronics shop which has designed an Arduino variant specifically for working with radio modules based on the nRF24L01 and similar pin-outs - traditionally too fine a pitch for breadboard work. The RFToy is fully open, with source code and hardware design files available via GitHub, while an introductory video is available on YouTube.
So in essence, RFToy is a 8MHz Arduino with buttons, OLED display, battery holder. It’s compact (1.5″ x 2.3″) and it’s suitable for a variety of projects involving RF modules.