Pros
- Very sustainable in lanes and jungle due to Consume (Q)
- Excellent harrass capabilities due to Ice Blast (E)
- Very good support role due to Blood Boil (W)
- Ultimate is capable of destroying team fights if positioned and times correctly
- Can jungle without recall multiple times, because comsume creates sustainability

Cons
- Absolute Zero (R) can be easily interupted and cause little damage, causing loses in team fights
- Absolute Zero can be hard to postion and use correctly

Primary Summoner Spell

Smite
This is the must have spell when jungling, although comsume does similar damage having both can help decrease jungle time and help with effecienc to ensure more ganks and harass.

Secondary Summoner Spells

Flash
Flash is my main choice due to the combo of Absolute Zero and flash to quicky surprise enemies and initiate team fights or end them :P


Ghost
Also one of my choices helps to get around if you are not recalling as much more towards the start of the match and you need to help teammates via ganking, also helps if you get caught in a teamfight and need to run, this with the combo of you Ice Blast (E) can help for an easy get away.

Teleport
Teleport may help just as much as ghost, with the extra feature of being able to teleport to specific ward, etc. So this allows for instant positioning, which may be better than ghost.

Choose whatever Secondary spell fits your wants and how you like to play Nunu, but I would always sugget to take smite unless you are really sure of your skill, and even then I would suggest it to increase jungling effeciency.