I've done some competitive battling, but only with a few random EV'd Pokemon thrown together. So I spent some time planning a team, and I'd like some opinions and advice.
Ferrothorn @ Rocky Helmet
Nature: Relaxed [+Def, -Spe]
Ability: Iron Barbs
4 Atk / 252 Def / 252 SpDef
-Power Whip
-Stealth Rocks
-Spikes
-Leech Seed
Ferrothorns main purpose is to lead off and set up entry hazards, as well as serve as a wall. Leech Seed is to restore health, and Power Whip is for a decent STAB attack. Rocky Helmet is to deal extra damage against physical sweepers.
Jellicent @ Leftovers
Nature: Bold [+Def, -Atk]
Ability: Water Absorb
248 HP / 216 Def / 44 Spe
-Surf
-Will-o-Wisp
-Recover
-Taunt
Jellicent is my spin blocker, as well as a supporter, being able to cripple physical sweepers with Will-o-Wisp. Taunt is to mess with Pokemon that rely on status moves. Surf is a STAB attack, and Recover is self-explanatory.
Starmie @ Life Orb
Nature: Timid[+Spe, -Atk]
Ability: Natural Cure
4 HP / 252 SpAtk / 252 Spe
-Rapid Spin
-Ice Beam
-Surf
-Recover
Starmie is one of my special sweepers, who doubles as a spinner. Standard Smogon set. I went with Life Orb over Leftovers as I'd like to hit hard once any entry hazards, as well as being a regular special sweeper should my opponent not use entry hazards.
Mamoswine @ Choice Band
Nature: Jolly [+Spe, -SpAtk]
Ability: Snow Cloak
4 HP / 252 Atk / 252 Spe
-Earthquake
-Icicle Spear
-Ice Shard
-Stone Edge
CB'd Mamoswine is my main physical sweeper. I went with Icicle Spear over Icicle Crash to break substitutes, and potentially deal damage in the one turn. Ice Shard is for revenge killing, Earthquake is a powerful STAB move, and Stone Edge is for extra coverage.
Salamence @ Leftovers
Nature: Jolly [+Spe, -SpAtk]
Ability: Intimidate
240 HP / 16 Atk / 252 Spe
-Rest
-Sleep Talk
-Roar
-Dragon Tail
Dual-phazing Salamence I saw someone on YouTube use. When it reaches low health, Rest to restore health, then Sleep Talk will give a 2 in 3 chance of phazing out the opponent, causing damage via Dragon Tail (if it's used) and entry hazards.
Zapdos @ Life Orb
Nature: Timid [+Spe, -Atk]
Ability: Pressure
4 HP / 252 SpAtk / 252 Spe
-Thunderbolt
-Heat Wave
-Hidden Power (Ice)
-Roost
Special sweeper Zapdos with Fire, Ice and Electric attacks has near perfect coverage, being able to deal at least neutral damage to every Pokemon out there. Roost is to restore health, and keep it going.
I welcome all feedback regarding my proposed team. Also, if you have any nicknames for any of the Pokemon, I'd love to hear them. Thanks =D

Ferrothorn @ Rocky Helmet
Nature: Relaxed [+Def, -Spe]
Ability: Iron Barbs
4 Atk / 252 Def / 252 SpDef
-Power Whip
-Stealth Rocks
-Spikes
-Leech Seed
Ferrothorns main purpose is to lead off and set up entry hazards, as well as serve as a wall. Leech Seed is to restore health, and Power Whip is for a decent STAB attack. Rocky Helmet is to deal extra damage against physical sweepers.

Jellicent @ Leftovers
Nature: Bold [+Def, -Atk]
Ability: Water Absorb
248 HP / 216 Def / 44 Spe
-Surf
-Will-o-Wisp
-Recover
-Taunt
Jellicent is my spin blocker, as well as a supporter, being able to cripple physical sweepers with Will-o-Wisp. Taunt is to mess with Pokemon that rely on status moves. Surf is a STAB attack, and Recover is self-explanatory.

Starmie @ Life Orb
Nature: Timid[+Spe, -Atk]
Ability: Natural Cure
4 HP / 252 SpAtk / 252 Spe
-Rapid Spin
-Ice Beam
-Surf
-Recover
Starmie is one of my special sweepers, who doubles as a spinner. Standard Smogon set. I went with Life Orb over Leftovers as I'd like to hit hard once any entry hazards, as well as being a regular special sweeper should my opponent not use entry hazards.

Mamoswine @ Choice Band
Nature: Jolly [+Spe, -SpAtk]
Ability: Snow Cloak
4 HP / 252 Atk / 252 Spe
-Earthquake
-Icicle Spear
-Ice Shard
-Stone Edge
CB'd Mamoswine is my main physical sweeper. I went with Icicle Spear over Icicle Crash to break substitutes, and potentially deal damage in the one turn. Ice Shard is for revenge killing, Earthquake is a powerful STAB move, and Stone Edge is for extra coverage.

Salamence @ Leftovers
Nature: Jolly [+Spe, -SpAtk]
Ability: Intimidate
240 HP / 16 Atk / 252 Spe
-Rest
-Sleep Talk
-Roar
-Dragon Tail
Dual-phazing Salamence I saw someone on YouTube use. When it reaches low health, Rest to restore health, then Sleep Talk will give a 2 in 3 chance of phazing out the opponent, causing damage via Dragon Tail (if it's used) and entry hazards.

Zapdos @ Life Orb
Nature: Timid [+Spe, -Atk]
Ability: Pressure
4 HP / 252 SpAtk / 252 Spe
-Thunderbolt
-Heat Wave
-Hidden Power (Ice)
-Roost
Special sweeper Zapdos with Fire, Ice and Electric attacks has near perfect coverage, being able to deal at least neutral damage to every Pokemon out there. Roost is to restore health, and keep it going.
I welcome all feedback regarding my proposed team. Also, if you have any nicknames for any of the Pokemon, I'd love to hear them. Thanks =D