Arauna is a real-time ray tracer developed for game development. Being a real-time ray tracer, it is experimental, and does not yet deliver the performance needed to produce graphics of the same quality as modern games do using a GPU. However, in its class, it is one of the fastest (probably the fastest) renderer. Two games have been developed already using Arauna, both by students of the IGAD program of the NHTV University of Applied Sciences (Breda, The Netherlands).
More information and download HERE.