Sorry Pilou, I didn't notice that you had already mentioned Blender. Well, it doesn't hurt to mention it twice.

Next to Blender's Cycles, my other favorite renderer is Keyshot, mentioned many times in this discussion already. I agree that the full version is too costly, but I've got the very affordable ZBrush-connected license. I use it mainly to render ZBrush creations, but sometimes I use ZBrush as a bridge between MoI Obj export and Keyshot.