One of the lines he says when PROJECT: Yi activates Highlander

(EDIT: Sorry, direct link led to the wrong item. My apologies for the mixup, I can't seem to edit the link properly. The actual page is below.)

And the way he says

"This will be... your final lesson."

...is so astronomically beyond my coping of awesome, I just, I hope he says this out loud, even as a global line. Loudly. As in, "Eternum Nocturne when he ults" loud.

For those who haven't yet checked these out (scroll way down past the lore to the "quotes" section, under when he activates Highlander, under the PROJECT tab):

http://leagueoflegends.wikia.com/wiki/Master_Yi/Background