A big, powerful and expensive breaker that works best if you look at ice through a shaper lens. Shapers have cards like Escher and Inversificator to alter the layout of servers. With them you could arrange a heavy piece of ice to be behind an easily broken code gate (or something Egret made into a code gate).
That does suppose however that there's heavy nasty ice that justifies the high cost of Mass-Driver. In the current meta that's far from guaranteed. And since Mass-Driver and its support cards pretty much require a deck to be built around them that's rather a big problem.
Maybe I'm just being grumpy but I don't really see a way to make Mass-Driver reliable enough to be worth the high cost.