What Pokemon should you choose?

Answer 1

You should have at least 1 or 2 tanks (Pokemon with good defense but has also good attack) .

A Special sweeper and a Physical sweeper which if you can use great you can 0-6 someone even in Uber rank.

Its very good to have a wall (a Pokemon that has crazy huge defense and special defense that can heal itself) .

Another option is to have a baton passer which can raise stats soaring high and baton pass it to another Pokemon).

You could also have an annoyer which i don't recommend unless you want to play with friends or competitively.

Examples for each one are

TANK: Rhyperior, Swampert, even Tyranitar and Dragonite are possible

SPECIAL SWEEPER:Alakazam, Gengar, Typhlosion

PHYSICAL SWEEPER: Salamance, Garchomp, Gyarados

WALL: Bastidon, Blissey (kind of a sponge wall), Dusknoir

BATON PASSER: Mew, Absol, Clefable, I think Togekiss

ANNOYER:Crobat, Gengar, Tentacruel

Also choose items wisely such as: Life Orb, Choice Scarf, Expert Belt, Focus Sash, Choice Band,Leftovers, Heal Bell, Salac Berry, and Choice Specs are great and items such as: Charcoal, Mystic Water, Sharp Beak, etc should be avoided.

By the way you should also choose Pokemon that appeal to you because its important to have Pokemon you like.

I hope this was helpful for you.