This is my purely tank, with a hint of support build.

I believe the Rune I have selected make Alistar the tank he is. With this build plus his ult, you can go in and pretty much take all the focus while your team destroys the other team. While also keeping your team alive with Ali's CC and heal (his ability and summoner spell.)

These Masteries are all based for straight taking most of the damage in a team fight, being as disruptive a possible, saying alive and keeping your team alive.

This build I have tested many times. I shuts down almost every AD carry that uses Attack Speed to do their damage (I.E. Vayne, Master Yi, etc.) I also would like to say, if the team you are fighting against has a ton of CC, then instead of going for Ninja Tabi I would say go ahead and shoot for Mercury Treads

I have also used this build a few times in Ranked matches, and I feel it is quiet relevant weather you are playing or regular matches.

Pro's

-Takes little Damage from Minions and Towers. Great for pushing lanes, and tanking towers.
-Great CC and if played right can turn a team fight in your favor.

Con's

-Goes through Mana fast.
-Does not deal great amount of damage (but this guide is more for the tank side)