I have always liked the concept of a anti-tank rifle. It is just so novel, I mean launching a massive round at a tank from the shoulder, what could go wrong there? Personally I think one of the coolest ones are the PTRS-41, just because it combines anti-tank sized rounds, with semi-auto capacity (its basically a massive SKS), and mannlicher style clips (en-bloc clips).

The problem with anti-tank rifles (for the civilian shooter) in all calibers other than .50 cal is that it is next to impossible to be able to shoot them. A huge amount of time, effort, and money has to be made just to acquire brass, bullets, and primers. Not to mention the need to buy a specialized press and dies. It is definitely a serious commitment to get one up and running.