Answer:
LEDs (they can heat up, but they do not require heat to emit light, usually heat is an unwanted effect)
Light-emitting field-effect transistors (same consideration as for LEDs)
Fluorescent lighting and generally cold plasmas that can emit light.
Old TV and PC monitors (ie cathode ray tube screen - although the light emission itself does not require heat, the cathode itself that shoots the electrons does)
Chemo-luminescence (like fluorescent sticks)
