I'd be interested in a combination of targetted skill, that you can then drag to direct the line of effect. Like Lulu E+Q. Alternatively, something like Janna's tornado, except you don't need to cast it from yourself. You could also cast based on terrain, something no champ really does other than Nautilus somewhat. Or a spell that follows your mouse cursor for a while (like, every .5 second puts thorns where your cursor is).
I would like to be able to play LoL with a shovel, though. I would consider that something never seen in a MOBA before.