Adafruit RGB Matrix Shield for Arduino

RGB matricies are dazzling, with their hundreds or even thousands of individual RGB LEDs. Compared to NeoPixels, they've got great density, power usage and the price-per-LED can't be beat. But...(isn't there always a but?) You need to use a special library to control them and they require a bunch of wires to be plugged in. Tougher than a single-wire connection for sure.