I like it when Jean simultaneously accessed Cable's tk and used it to not only change their outward appearances along with her tp to supress how they would normally act, but she also made the change so complete and to such an extreme that even scanners couldn't tell they were mutants.

Also loved it when Jean stopped Rictor's heart.
Some other cool instances:

... when she blew up Fitzroy's undestructable armor.

...when she was able to track an electronic brain.

...when she super-charged her teammates and absorbed their physical and mental exhaustion allowing them to be at their max pretty much indefinitely.

...when she projected her astral form half way across the world and still use her tk on the molecular level through the astral form, even creating a brand clothes for Storm.

...when she telepathically froze Apocalyspe!

...shut down nerve endings to spare Candy Southern pain.

....projected an illusion in Magneto's mind that even his helmet and defenses didn't help against.


I could go on forever....lol.