Lux + Thunderlord's Decree
As much as love the extra burst on Lux, I can potentially see annoyance about this later, So I'm gonna call it.
Lux's interaction with Thunderlord's is not very... fair. Lux's Illumination Passive with the keystone, as awesome as it is damage and all, shouldn't add to the stack of Thunderlord's.
E + AA and ending the trade there can pretty much bruise the enemy mid laner, and once a few levels are gained and a bit of AP is bought, can pretty much put the enemy on tilt with how easy the damage done is. Rinse and repeat once Thunderlord's is up and you've got an annoying laner. Or much more depending on how much you hate Lux.
One spell and one AA isn't enough of a commitment for Thunderlord's to proc. As much as I love me some lasers, early game interaction can be pretty much cut at half of her rotation.
Also that 45% Cdr is really niiiiiiice~ And DFT lets Lux know whether or not she hit something with her Q stealthed or in the fog. Use that with what you will.
QW/QE/QAA
QW
EQ/W
These are off the top of my head. To be honest, I don't really mind at all.