There was an engine years ago featured in the aviation magazines called the dyna-cam engine. It had numerous small pistons set up in a crankcase that looked like a revolver, and a sister bank connected at a 45 degree angle. The gist on that engine was that it was quiet, nearly vibration free, and had a torque curve as straight as an arrow. Never made it to market as far as I know.
The ball engine here in this thread looks neat. It's not a wankel engine, but somewhat near the idea. The wankel engine was great for snowmobiles - especially if you were pulling a tag-along full of kids. The torque on the wankel engine made pulling power like no tomorrow.... Prof