As a collector, take note of the following: 1
This ability triggers for each attacking non-human creature, which is why its so deadly
The most powerful decks of the past formats have been those capable of setting up a checkmate situation (Yata), swarming the field with monsters (Teledad, Lightsworn), or just executing a combo to leave the opponent without resources (Wind Up, Infinity w/Thrishula)
It works fine with being turned on before the match starts and remaining on after the match
Plus, some cards (such as [c]Ox of Agonas[/c], which well see later down this list [spoiler!]), work better from your graveyard, so discarding them wont even feel like a downside
You can only use this effect of "XYZ Hyper Cannon" once per turn