Lee Sin and Nocturne.
Nuff' said.

Captain Trymo.

http://c.asset.soup.io/asset/2355/5148_0714.jpeg

Also Ashzreal ult.
Enchanted Crystal Barrage.

It stuns everything it passes through, dealling less damage as it passes through enemies and stunning longer the further it flies. THE ULTIMATE UTILITY ULT!
Do you want to stun longer for allies in team fights? ult from spawn.
You wanna damage? ult their face in.

Karthus and Gangplank.

All enemies have a Gangplank ult come down on them while the Karthus ult is charging.

Malzokai
Sets up a area suppressing all enemies inside, when detonated deals massive damage to all champs inside over 2.5 seconds. Ult can be sustained till Malzokai runs out of mana, or is slain.

Fiddlesticks&Anivia
Super AOE

Tryndamere&Kayle
7 seconds of immunity

Ashe&Ezreal (/Darius)
Skillshot that reaches the whole map

Shaco with TF
Taco Fate

Ult: Reveals entire map for 1 minute, 'r' to spawn a clone anywhere on the map, a clone will attack the nearest enemy immediately and chase forever, clones last 20 seconds and have a 10 second cooldown.

Soroka and katharus:
All enemys take 450/550/650 Damage and all Living allies are healled for a precent of the damage taken by all enemys (ex. 3250/4= amount healed by allies excluding kathorka)
ULTIMATE SUPPROT

Katarina and Ashe

the ult shoots ten arrows scaling off ad/ap and hits 3 different people stunning them every time and slowing others around

Nidalee and Jayce.

Transform while you transform? I have no idea how that'd work out.