Before you vote this down saying "Veigar isn't a tank, what a dumbass", hear me out. Think of Veigar in a different perspective, he is going to change the way you think of tanking, I can guarantee that.

LETS GO!!

Veigar works almost the same as Amumu, but with a much higher damage output, more constant team stuns, and an amazing ability to rid of enemy AP champs. The items up top vary like this, #1 is my general build for a balanced enemy, #2 is focussed to destroying AD heavy teams, and #3 is focussed for AP heavy teams.

Pros:
Amazing team stun
Supports the team beyond belief well
Still does amazing damage
Can destroy AP champs with his ulti
Insane HP per 5
Insane survivability
Basically makes a team 5 DPS but still impossible to kill

Cons:
Can't full nuke a 3.5k hp champ like with AP
Won't be able to get 1000 AP (lol)
That's literally it

My build for a balanced enemy team. In the end you will cap at about 4000 hp and an HP regen of about 120 per 5 seconds! You should, if you are last hitting minions well, end off with about 300 AP also, which is amazing.

Items!
These are the general items I would use. There are, however, replacements for most items. An amazing replacement for the Warmog's is a Sunfire Cape. It helps quite a lot. You can also switch other things around depending on what your looking for, but this build is generally all you need.

Build #2 is for an AD heavy enemy. You will literally be insanely hard to kill and will be stunning them out the ***. I have used this build on multiple occasions and refused to die while getting more assists then anyone and the second highest amount of kills.

Build #3 is for an AP heavy team. Again it will make you insane to kill and generally awesome.

General items that can be added to all builds can include this on the lines of Mercury Treads and Banshee's Veil. There are more items that can easily help you out but it is at your discretion and depends on the enemy team.

It is really funny how you play tank Veigar. It is similar to playing Singed, you constantly run around pounding damage on the enemy, stunning them in the opportune situations. If they do focus you they will quickly realize how stupid that was. He is funny to play and is amazing in team fights.

Pretty straight forward. The HP regen based on mana is amazing seeing you will have a high amount of mana and it will contribute greatly to your HP per 5

Truthfully, I believe Veigar is better as a tank then a nuke for your team. A nuke veigar kills one person then is quickly destroyed whereas a tank veigar is constantly pounding off damage and full team stunning with arguably the best stun in the game. Thanks for reading my Veigar tank build, I think you will all see why I love him this way soon.