In the first book, Thrawn gets cloaking shield technology, but ships using the cloak can't see through it with their sensors or communicate with outsiders, so they're completely blind and deaf. Being Thrawn, he still comes up with brilliant plans to use the technology to great effect:
Thrawn attacks New Republic convoys, limiting the number of freighters the New Republic has, so Ackbar has some surplus capital ships converted into lightly crewed transports at the shipyards of Sluis Van. Thrawn then steals mole-miners, puts them in the cargo bay of a freighter with some TIE fighters and hides the inside of the ship with the cloaking shield. He brings the ship into the Sluis Van system, blows it up and releases the mole miners to burrow into the hulls of the converted capital ships, inserting four or five stormtroopers to kill the skeleton crew and seize control of the ships for his own use. This plan only fails because Lando Calrissian happened to be present, and even then the New Republic ships end up being badly damaged so Thrawn still benefited to some extent.
Thrawn has two cloaked Carrack cruisers towed into position just under where a planet's planetary shield will be when it's switched on. He then openly comes in with the Chimaera and they raise the shields. He fires at the parts of the shield that the hidden cruisers are situated under and gets Joruus C'baoth to use his Jedi powers to communicate through the cloak so the crews of the ships fire at the planet exactly in time with the Chimaera`s shots hitting the shield. From the planet's perspective, it looks like the Chimaera has a new superweapon capable of passing straight through they shield, and they promptly surrender.
To neutralise Coruscant, Thrawn has 22 asteroids fitted with cloaking shields, then brings a fleet of ships into orbit of the planet and has them use their tractor beams to fling the cloaked asteroids into orbit. But he also has them run a power surge through their tractor beam emitters many dozen more times (which, as the asteroids are invisible, is indistinguishable to the New Republic from launching a real asteroid). The result is that Coruscant can't risk lowering its planetary shield in case an asteroid hits, but has no idea exactly how many asteroids were launched, so has no way of knowing if it's accounted for them all or not.
It's offscreen, but Yoda's fight with the Dark Jedi was pretty clearly this.