It's got to be last year. Nintendo were going in struggling and the news that they'd not be giving a traditional conference was ringing round the gaming world causing quite a stir. Cue the day and then on walked Iwata to fight Reggie and that really set the tone for the rest of the show. Splatoon came as a huge surprise to everyone and the ingenious Treehoue event created joy and intrigue for the rest of the week like never before.
I do desperately hope for a similar performance, because it was just amazing.