Rechargeable LED Glowing Badges
These acrylic badges can glow in one of seven colors, or be set to either fade or flash between the colors. They recharge via a Micro-USB port on the side (and you get a tiny Micro-USB cable too). They also come with a clip, as well as a fairly basic lanyard.
Very bright, they'll run for 5 - 6 hours on a full charge!