Elise untargetable on fountain
 

Using the DeathBlossom skin.

I cast her repel on a Lux fleeing onto her fountain. When I repelled down on her the 'laser' did not attack me. I was free to run around up there attacking the enemy team until they managed to kill me. I was already low health, so I did not get a chance to test various things like...

1) If walking off the fountain then back on would allow the laser to target me.
2) If casting repel again would allow it to target me.
3) If the bug happens when repelling onto other champions.
4) Not sure if Lux had her shield up or if it would matter.
5) I casted repel on Lux to get into the air. So casting it on the ground, and then repelling onto the fountain may or may not cause the bug.