Since we are a website focused primarily on commissioned indoor graffiti & mural installations, we are only ranking water based acrylic spray paint at this time.  In our opinion, this is the future of spray paint due to the low odor which makes the product ideal for interior installations and live events.  For large scale outdoor murals, there are a lot of brands out there that we are not considering in this ranking.

#1  MTN300 (Water Based 300ml Spray Paint)

Probably the best water based spray paint on the market at the moment.  Unfortunately, it only comes in a smaller 300ml can size.  "Low odor, resin based, water soluble spray paint. Suitable for both indoor and outdoor use since they are water resistant once dry."  Check out more information on their website:
​http://www.montanacolors.com/webapp/spray?id=560

#2  Sugar Artists' Acrylic

Higher pressure than the MTN Water Based 300 above.
"A revolutionary health conscious formula, with high performance capabilities. Sugar is unlike any aerosol product you’ve ever used. The world’s first hybrid water and alcohol based acrylic aerosol paint. Sugar is harvested specifically to deliver the highest quality results for artists, with the lowest possible impact on your health and our environment."
Website: http://sugarartistsacrylic.com/about-sugar