The one hit, I think the NHL could benefit from taking out of the game is the one behind the goal line. There's been way too many head injuries over the last 10+ years. The players have become much faster and powerful skaters and every time a puck is dumped into a corner, it becomes open season on a defenseman.
If their serious about protecting players and eliminating head injuries, this should be their first step.
I love a clean open ice hit, but truth be told there's only a handful of players who know how to deliver one. Its a lot easier to dump the puck in the corner and try to take a guys lively hood away from him by running him through the boards. The NHL has a great product, the fastest most exciting sport going and they need to do a better job of protecting their assets.