My best Tyranitar went like this:
Leftovers
252 Hp / 252 Att / 4 SpD
- Crunch
- Protect
- Stone Edge
- Thunder Wave
I really like protect on him. Tyranitar has like, a million weaknesses. You don't know what the enemy will try to use on you when they switch in. The easiest way to find out is to just use protect (provided you know they aren't going to buff themselves instead).
For example, say you have Tyranitar in the field. Enemy has a Crobat out. This Crobat is either going to Giga Drain, or U-turn. Either of which will hurt Tyranitar about 1/4 hp. I don't know which it's going to be. So I use protect. Crobat uses u-turn.
So now I know what the enemy is going to do. I can thus switch in a steel or fire type next turn for very little damage instead or I can tank the damage, and make Tyranitar use thunder wave to immediately cripple the enemy that's switching in.
Another example is when Tyranitar is out in the field again and say the opponent sends in something weird... like Manectric. Under normal circumstances, you might be going... "okay... what the fuck is going on?" Since I know this bastard is up to something, I use protect to see what exactly it is. Manectric uses switcheroo and fails. So now I see his stupid plan. That exact scenario has happened quite a number of times. A non-protect Tyranitar would have been choice spec locked.
I also love thunder wave on him simply because Tyranitar does gigantic damage, but only has middling speed. However, if the opponent is paralyzed, then Tyranitar will eat their face. It's my number one method of dealing with Mega Charizard Y. First turn they use solar beam, I tank it and survive on low hp. I apply thunder wave. Next turn they die to stone edge (or I use protect to heal myself before killing them.)