Arnold is an advanced Monte Carlo ray tracing renderer built for the demands of feature-length animation and visual effects movies. Originally co-developed with Sony Pictures Imageworks, Arnold is now used at over 250 studios worldwide including ILM, Framestore, The Mill and Digic Pictures. Arnold was the primary renderer on dozens of films from Monster House and Cloudy with a Chance of Meatballs to Pacific Rim and Gravity. It is available as a standalone renderer on Linux, Windows and Mac OS X, and is accessible through plug-ins for MayaSoftimage and Houdini.
 
 
More info on: http://www.solidangle.com/arnold/
Here you can download the trial: http://www.solidangle.com/arnold/try/