Extrasensory is a very good move, however it is learnt by only a few pokemon via breeding and I believe (but not sure) that only Shiftry learns it naturally.
So does Nuzleaf. (well gee that helps--Shiftry evolves from Nuzleaf...) I wish Ninetales could learn it, but...
Anyways, some of my favourite moves are:
Curse--This is probably my top favourite move. I'm talking about the ghost version, not the one that makes Snorlax so overused. It's a perfect move to use on a trainer's last Pokemon. I especialy do this to gym leaders, since they usually use their best Pokemon last. Ahh, I remember that time in Gold when my Gastly used Curse on Whitney's seemingly-all-powerful Miltank, and I just hept stalling with my Pokemon until Miltank's afflictions caused her to faint... Mwahahahaha.
Magical Leaf--I like this attack simply because it's pretty. One of the reasons why one my best Pokemon in Sapphire is Roselia is because Roselia learns it. And another thiing I like is a couple of Psychic Pokemon can learn it, such as Kirlia and Mr. Mime.
Will-O-Wisp--Another attack I like for its looks. I especially like the way Phantom's Dusclops used it in a contest in the anime, it looked cool there... Anyways, aside from that, an attack that simply causes a burn? That's pretty darn good. My Banette and Ninetales proudly know it.
Hyper Beam--I don't care how bad people think this move is. 150 is a pretty powerful damage, and if used by a physical sweeper, it can most likely KO a Pokemon, and then you can switch out. I've loved this attack ever since Lance's Pokemon kept using it on mine in Yellow...
Dream Eater--It's such a powerful move (100 power), and it drains HP too! I really can't see why Hypno doesn't learn this by leveling up... because every Hypno I ever had knows this move, and of course Hypnosis as well.
Teleport--It's a great replacement for a Smoke Ball, especially if you have it on a speedy Pokemon like Alakazam. And plus, it's a great field move--you can return to a Pokemon center from anywhere outside. It's perfect if your Pokemon gets poisoned and you don't want it to faint by walking.
Confuse Ray--100% accuracy is pretty darn good for a status changer. The only thing I hate about it is when my own Pokemon gets hit by it--ARRGH!
Take Down--Lots of Pokemon learn it, and it's a great contest move--especially if the Pokemon also knows Harden and goes last. In a combo it gets... 12 appeal points!! (I also like Hi Jump Kick for this reason, when combined with Mind Reader, but only Hitmonlee and the Meditite family learn that combo...)