Car/Boat equipment
Radio, lights, pumps etc designed for boat use - can run on 14/15v etc
Consumer equipment
Rated 12v PSU, regulated or unregulated? Potential problems, at own risk...
Laptops PSUs
Lighting
Flourescent - basic area lighting - 8/16W tubes
LED - v low energy (1-2W), small area, more expensive, good for reading light etc
Halogens/Tungsten - 12v so tempting, but energy heavy (20-50W each)
Inverters
Keep an eye on load, turn off when not in use, small vs big, earthing/RCD.