Lopunny - Ability:Klutz - Move:Switcheroo - Works well with Burn\Toxic Orb.
Machamp -Ability:No Guard - Move:DynamicPunch - BIG Damage and a chance of confusing that won't miss!
Marowak,Golem,etc - Ability:Rock Head - Move - Double Edge - 120 Damage and NO recoil!
Electrode,etc + Ghost-Type - Move: Explosion - 250 Damage and your Ghost-Type Ally won't get hurt!
Tyranitar,etc + Flying-Type - Move-Earthquake - Damage opponents BADLY but won't hurt your flying-type ally.
A Pokemon Team Strategy Example
As a Psychic-type,Mr Mime is weak against Dark-Types,that's why Pinsir is there,it's strong against Dark-types as it is a Bug-type,but Pinsir is weak to flying-types,so you send in Glalie as it is strong against flying-types.If your opponent switches to a fighting type to defeat your ice-type Glalie,you send in Mr Mime again.If you build a team this way,you'll be prepared for your opponents' weaknesses even as you guard your own.