You must assemble a 7-person team to combat attacking aliens.

[VoidWanderer]

Ripley and 6 Marines

 

[Bravo 21]

Garrus(Mass Effect)
The Emperor(40k)
Captain Jack Sparrow(Pirates of the Caribbean)
Batman (The goddamn batman)
Heavy Weapons Guy(TF2)
Greg Jennings('cause he put the team on his back, do)
V (V for Vendetta)

but honestly, all you need is one of these people, they are all that awesome.

 

[NerfedFalcon]

"Serious" Sam Stone (sledgehammer, auto rocket launcher, minigun, laser gun, cannon. Also has ample experience fending off hordes.)
Travis Touchdown (more melee-focused than Sam, but no less skilled at taking out hordes.)
Heavy Weapons Guy (able to turn his opponents' weapons into more bullets for his minigun.)
Rico Rodriguez (grappling hook up to vehicles, plant some C4, pull infinite parachutes out of ass a second before hitting the ground, unhurt. Sound like a plan?)
Dovahkiin (Magic+melee+bows+FUS RO DAH!!!!!! etc=killing spree.)
Reimu Hakurei (so it's not a sausage party. And she kinda kicks ass. Unlikely to kill anything herself, but she'll take home the assist ribbon, easy.)
The Medic (keeping everyone alive, particularly the Heavy.)

 

[Auron225]

Chuck Norris
6 recently hatched ducklings

Poor aliens...

EDIT: Or, the Cullen family from Twilight. They wouldn't win, it'd just be worth the earth to see them get taken down by aliens X)

 

[Dalek Caan]

Master Chief,
Commander Shepard,
Sovereign,
Ratchet,
Iron Man,
Garrus,
Tali.

Aliens don't stand a chance.

 

[The Salty Vulcan]

Spoiler

Sherlock Holmes

Mitchio Kaku

Chell

The Doctor

Teddy Roosevelt

Marvin the Android

Paarthurnax

Do I win?

 

[Jetut]

The Anrgy Video Game Nerd.

Samuel L Jackson.

Big Boss.

Chuggaaconroy (His puns are deadly.)

Freddiew.

Jason Voorhees.

Natsu Dragneel.

 

[C F]

Samus Aran (Expert at incorporating foreign tech)
Gordon Freeman (Primary tech expert)
FE9&10's The Black Knight (Primary defensive, unstoppable tank)
Master Chief Petty Officer Spartan-117 (Primary offensive)
Darth Revan (Secondary offensive, healing and Jedi support)

At this point, I don't need anybody else, but I'm going to add:
Dr. Brackman (Mission Control)
Commander Shepard (Diplomat)

Any alien threat will regret going toe-to-toe with this group.

 

[MammothBlade]

Major Motoko Kusanagi - Commander, Stealthy Assault Cyborg, Hacker
JC Denton - Stealthy Assault Cyborg, Hacker
Saito - Master Sniper
Uryuu Minene - Explosives Expert, Future Diary User
Laxus Dreyar - Lightning Commando
Lucy (Elfen Lied) - Psychic Commando
Joker - Ace Pilot

Their main transport would be SSV Normandy + Mako.

Master Chief,
Commander Shepard,
Sovereign,
Ratchet,
Iron Man,
Garrus,
Tali.

Aliens don't stand a chance.

Except half of your team are aliens, and at least one is pure evil

 

[XMark]

Twilight Sparkle
Rarity
Applejack
Rainbow Dash
Fluttershy
Pinkie Pie
Spike

Defeat the aliens with the power of FRIENDSHIP!

 

[Wintermoot]

The Doctor
he has experience and can probably resolve the invasion without unnecessary bloodshed.

Dr Who

please be trolling