Thanks a lot for the feedback, I really value it and once I've finished my Lee Sin guide I definitely will be *****ing up this one :)
I really think this guide was just a bit of an experiment to see how I should format a guide etc. being my first! But I still would like to improve it in anyway possible so thank you very much again.

Items seem not too good, and the guide is too wordy.

Examples include Rod of Ages > Rylai's Crystal Scepter. All your offensive skills slow a lot already. Extra slow won't help too much (Nunu has one of the strongest and most reliable slow in the game), and the mana and slightly more HP helps out more.

I would rather not take Will of the Ancients too. The only situation it actually becomes gamechanging besides the AP and aura is when you left a tiny bit of health, charged full ult, and smash your opponents' faces. That's very very rare.

Runes should be specialised to be most effective. Your sets of runes are too varied to provide a good boost to any one stat nor is it widely spreaded enough to give an overall boost. PS : Magic Pen marks may be better than health, especially since Nunu's jungle is seriously the easiest among most junglers. The MPen helps much more later.

As for masteries, I suggest not taking jungler-based masteries such as Tough Skin and Bladed Armor . Runic Affinity is possibly good, but that means you plan to take lots of buffs or kills. It all depends on perspective. Do you think you can help to carry the team partially? If yes, you should take 9 in Offensive Masteries for the Magic Pen. If no, you should really give buffs after initial jungle period. I don't find Summoner's Resolve too good, since it only boost 10 gold per smite, which is 70 seconds. Lets say you always spam it. In 7 minutes, you used it 6 times. By the 30min mark, you used it 24 times, meaning 240 gold extra only (Take into consideration initial 1.55 second start). I'll rather save my smite for major buffs or creeps rather than spam it for a bit of gold. But that's my perspective, so you can choose to ignore it.

You have a slight disadvantage as a jungler. While you have to wait for level 4 for your Ice Blast, others may already have healed to full or ganked. That may become a big problem, since you'll be counted on to put pressure on your opponents.

And finally, your guide itself. It has only 5 colours, red, green, black, white and yellow. It also has no pictures. For that, it would not be really interesting to read, so you may want to put in some pictures.

Do put in a few situational items as well. To see to pros and cons of each item may help players in the short run.

Hope it helps :)

Thanks a lot, I really appreciate the compliment and the feedback even more so!
I'll definitely get to finishing the items section tomorrow and revise the revolver/WoTA.
Thanks again,
Rev.

I liked it. My only concern is that revolver/will of the ancients seems unnecessary with him already having the consume heal. Use other guides as a basis and finish that item section ASAP. <3