Here’s an interesting pair that I came across at the Pentax booth at PhotoPlus 2012.  That’s the Pentax Q10 paired to the K-mount Pentax DA 560mm F5.6 ED lens via the Adapter Q.  The odd combo results in a roughly 3080mm reach compared to a full frame camera, which is due to the small 1/2.3″ sensor found inside the Pentax Q10.