If you already read my Udyr guide, you will know, that I posted an experimental build there, because only if you search for new builds, you will find the best. And so many unkown builds (Blue Ezreal, lol) got through testing like this possible and popular, before that, somebody would have flamed you for building that.

So, lets start with my first experimental build. I latelty was thinking about a super tanky top laner which has high base damage and great cc, but isn't really played there. I found one: Alistar. As you know, Alistar is normally played at the botlane as support, but I think, this could be a waste of his potential. I mean, his base damages (240+275) are really high, similar to someone like Dr. Mundo. Second, his ultimate is the best tanking tool in the game. Third, he has a knockup and knockback, do you need any better CC? And fourth, he deals magic damage, means he fits the new grow of magic damage top laners.

Beside this 3 spells, Alistar also has good AoE dmg if he is in the middle of a fight, thanks to his passive. His heal is rather bad but it is still there and gives sustain. I think he could be an unkillable force in the middle of a fight, dealing constantly AoE dmg. So, how to reach that?

I would say, the best item to get AoE is Sunfire Aegis, so this item would be definitly a core in his build. Second, the power Sunfire Aegis is normally low, except if you combine it with magic penetration. For this, items like Abyssal Mask, Sorcerer's Shoes and Liandry's Anguish exist. These would also fit Alistar well, since he has rather low, but still existing AP ratios. So, with all those items, the damage will be rather high, but defense is still missing. For this I would choose full tank items, as no more damage is needed. Perfect items would be Randuin's Omen, Runic Bulwark(sadly, this will be removed), Spirit Visage, Frozen Heart and Warmog's Armor. So you see, you got a good mix of options here. Buildwise I would follow the rule, get what you need. If you feel you got not enough defense, obviously defense has priority. But if you can survive the enemy with ease, you can build more on magic penetration items. The final thing after all this theroy, is a normal game build:

Starting items:

Item Sequence

Health Potion 50
Health Potion 50
Crystalline Flask 345
Health Potion 50
Stealth Ward 0
Boots 300
Stealth Ward 0
Health Potion 50
Health Potion 50

I would say, Alistar has here very many options. You can play him with wasting very much mana, but you can also play him rather save. I think, there is a perfect starting item for every situation.

Full Build:

Item Sequence

Sorcerer's Shoes 1100
Abyssal Mask 2400
Randuin's Omen 2700
Spirit Visage 2900
Liandry's Anguish 3200
Frozen Heart 2700

I would call Sunfire Aegis, Sorcerer's Shoes and Abyssal Mask core. You will buy them most likely in every game and most of the time in this order. There are exceptions, like a magic damage top lane enemy or such. Then you would go Negatron Cloak, Giant's Belt, Sorcerer's Shoes, Sunfire Aegis, Abyssal Mask. The rest of the items is very situational, but in a normal go, you will go after this amount of damage for pure defense, as you got enough offense by then. And finally, after that, you raise your damage again for lategame.

I hope I inspirated you to test something like this out. Why not post your own ideas on the same way for others to test?