All-tail jets
The biggest all-tail jets are the quads VC10 and Il-62.
Problems with tail engines include having the centre of gravity of airframe behind the centre of gravity of payload, and needing structural support to carry the weight from tail through the rear fuselage and into the wings.
Nevertheless, tail engines are the favourite arrangement for small regional and private jets.
There was the famous VC-10 trijet, with ordinary pair of low-bypass jets on one side, and a big high-bypass turbofan opposite. Would it make sense to reengine a VC10 to be a twinjet (another big turbofan instead of the other pair of low-bypass jets)?