I'd say that jutsu Itachi used against Kabuto(It was Izanami or something...can't remember the name) The reason being that this jutsu can help someone instead of just harming them, as when it helped Kabuto redisover himself.
I also like the flying rajin because it would be cool to move so fast and the chidori because...it's like lightning and it looks so cool.
I also like that sand tsunami jutsu, it looks so strong. That and the sand levitation one..the reason being that you basically get to fly
Pretty much all of the Rinnegan Jutsu are cool, same said for MS. Chidori is pretty cool. Katon: Goka Mekkyaku, and Katon: Goka Messhitsu (IIRC they were both Juubi-sized Katon), Adamantine Sealing Chains, Uchihagaeshi - I could go on.