I love playing nasus. Like I play him and im all like epic and stuff. Okay, but seriously Nasus can be great in whatever team comp you have. He has great AOE damage in team fights, has massive single target damage when farmed properly. After a few levels, he can jungle very efficiently. And he is very tanky whether or not you tank with him. Not even to mention he has an amazing slow that can mean death for almost anyone in game.

Tank Build

+ Very Tough
+ Great CC
+ Verstile against all damage
+ Massive damage for a tank
+ Great Chaser
- Poor initiator
- Can be easy to harass
- Poor SS farming can destroy his damage output
- Expensive first item

Tanky Build

+ Very tough DPS
+ Ungodly LS
+ Hits very hard very fast
+ Great AOE damage for a DPS
- Very vulnerable to CC
- Weak against AR

I pick runes and masteries that will allow me to be tanky while still putting out decent damage. There really isn't a whole lot of thought behind other them than that.

Obviously, itemization is very important. I am not going to list a separate section scenario build because these builds stand very well against almost any team comp. I'll justify that statement within this section.

Currently the best characters in the meta game are tanky one. This is because it is currently so easy to focus down squishies. The better teams will have good CC and tougher champs. Some sqhishies stay alright because of high escapability (Leblanc for one). If there are a number of nukes, the tank build has a great MR item as well as tons of HP. If they are tanky, yet again great AR items as well as tons of HP. You also have to account for Nasus' massive natural LS. Unless, a team is completely unbalance on one or the other side this tank build will be fine.

If they are completely unbalanced, they probably suck and you should beat them anyway. Shame on you if you lose to a 5 AP team ^_^. If it does happen, just grab a Thornmail or a Banshee's Veil respectively.

Since DPS characters tend to be more proactive than reactive the only thing I can say here is unless their is a massive hp champ like Vladamire or Dr. Mundo (substitute and item for Madred's Bloodrazor) then this build will be fine.

I have one thing to address here:

Siphoning Strike vs. Spirit Fire

While most say that Spirit Fire is better at farming (It is) I would go with Siphoning Strike. This will allow you better and more opportunities to farm your SS. As well, when an enemy is aggressive ( Katarina) give them a good whack and take 25-40% of their HP and they'll back off.

The only exception to this rule is if you are soloiong top. In that case, try to raise your SF first so you can get as much gold as you can while staying safe. I know you have almost no SS farming but its better than feeding. Trust me.

You should always be looking to farm this. After you have reached a decent level 4-5 and have sheen. You can jungle fairly quickly and easily. It is also extremely easy to farm SS. If you had a slow start and are having to hug your tower farm through the jungle when you can.

I cannot stress this enough. If you have properly farmed SS, YOU WILL DOWN TOWERS FAST. SS works on towers. You can down towers unbelievably fast. Most likely, faster than any other champ out there. When someone harasses you, don't give them free damage. Whack em once then back. I hate giving up free damage. Being worn down is one of the easiest ways to give an inferior player a free kill.

Regardless of your skill level. Nasus is fun to play. Nope really that's it.