The downward ejection sounds really nice. So far as the poll, I'd have to say most of the best guns, and that's not a choice. There are other great designs by other people.
Since I got my Sentinel, I've read up on Harry Sefried who did the original design, and many of the later refinements. Did the basic design of most of the later High Standard pistols, especially the Supermatic Citation. Later he did twenty years at Ruger. He designed the 10/22 rotary magazine, the original lockwork of the Six series revolvers, and totally designed the Redhawk. He had around thirty patents. That's a good track record.
Discuss .22 Rifles.