My friend just had a pretty fun Nunu rework idea

So basically, the rework will change two skills: His E and his R. So basically, his E will spawn a cluster of six snowballs at target location. Click the ground where it is, and your next basic attack will have 525 range, deal bonus damage and apply a slow to enemy. Snowballs can be thrown by you, your allies or the enemy. You can only hold one snowball at the time. Allies will only deal 50% of the bonus damage and not apply a slow.

Note: Champions with higher range than 525 on their basic attack can only trigger the snowball if they are within 525 range of their target.

His ultimate creates a snowfield in a huge area around himself for 10 seconds. While Nunu is holding a snowball on the snowfield, he will roll it. The snowball becomes bigger and bigger and deal increasing amounts of damage and slow. Throwing it will instead roll it in target direction. At maximum size, the snowball will deal area damage and stun anyone in the area. Other champions can not roll the snowballs they pick up. Similar to Twisted Fate's pick a card, you will have a maximum amount of time before your held snowball runs out.

The point of this is to cater more to Nunu being able to chuck snowballs, like his splash art suggests, instead of a random ice spell. His ultimate will no longer be an easy to stop ability. Instead, if you're able to walk around for a couple of seconds, you can roll several huge snowballs at the enemy, being a massive disruptor. His W will give his snowballs more oomph, and allow him to run faster, which makes the snowballs huge faster, so I want it to stay the same. His Q is fine as it is in my opinion.

The reason I want the snowballs to be able to be picked up by the enemy, is that you create a desired target for you to drop your ultimate on top of, making them question their decision to run over to it. Once you have a snowball and the enemy have a snowball, you have a snowball fight. Except your snowballs will obviously be more potent in your ultimate's area.

A funny interaction would be with Righteous Glory. Once you have a massive snowball, you can turn it on and basically run into your enemy to stun them. Remember though, even though the giant snowballs can leave the snowfield, they cannot be made bigger outside of it, so make sure to prepare your snowball ahead of time.