Tyranitar

Type Tier
Rock / Dark OU
Statistics
Stat
HP
100
403
Atk
134
366
Def
110
318
SpA
95
288
SpD
100
298
Spe
61
220
Name Item

Cursetar

Leftovers
Moveset
~ Rock Slide
~ Curse
~ Earthquake
~ Rest / Roar

Good ol' Cursetar, not very interesting but it does its job rather well. Curse up and proceed to sweep. Roar could help counter Steelix or Skarmory.

Name Item

Mixed Attacker

Leftovers
Moveset
~ Rock Slide
~ Crunch / Roar
~ Earthquake
~ Fire Blast / Surf

This set can seriously surprise a lot of things. And Tyranitar actually has enough Special Attack to hurt things with the special moves it has.

Name Item

Pseudo-hazer

Leftovers
Moveset
~ Rock Slide
~ Roar
~ Pursuit
~ Surf / Dynamicpunch / Earthquake

Different set here; works well with Spikes. Surf is for other Rock and Ground-types; if they try to switch out, Pursuit them. Also good for switching in on Alakazam. Dynamicpunch would be a risky variation due to the low accuracy, but it can be good for stuff that normally switches in against Tyranitar (like Ground and Rock-types) for the Confusion.

Name Item

Special Attacker

Leftovers
Moveset
~ Crunch
~ Hidden Power Fighting / Dynamicpunch
~ Fire Blast
~ Ice Beam / Thunderbolt

Special Tyranitar. Covers pretty much anything. Hidden Power Fighting/Dynamicpunch for Blissey and Snorlax. Precursor to the RS phenomenon of Tyraniboah.

Other Options

Just about everything is covered above. Although it might be interesting to know that there was once a Hidden Power Psychic fad! Screech is also an interesting move for Tyranitar, especially on teams that utilize Spikes.

Opinion

Tyranitar may be one of the most versatile Pokémon in this generation. Takes advantage of the highest Attack in the game with Rock Slide and Earthquake, enabling it to attack pretty much any Pokémon in the game due to the fact that nothing resists both of those types. It also gets STAB on Crunch, and it's got good Special Attack to support a variety of moves that can be used to confuse the opponent. Tyranitar also has sufficient defenses that very few things outside its 4x weakness to Fighting can OHKO it. A very versatile Pokémon indeed.

Counters

Suicune can take anything Tyranitar happens to throw at it, except a super effective Thunderbolt. Donphan, Marowak, and Heracross are all good switch-ins. Starmie and Slowbro (although Crunch lessens their effectiveness some), Machamp, Quagsire, Sandslash, and Umbreon are the others. Don't be fooled by the amount of counters this Pokémon has—for all these counters, the right moveset will probably deal with them accordingly.