The Avengers

Iron Man
Billionaire Playboy gets a message from Agent Coulson about Loki's attack

Captain America
Steve Rodgers just woke up from his 70 year nap and Nick warns him about Loki

Thor
As Loki's brother, Thor comes into the movie with some lighting.

Hulk/Bruce Banner
Bruce and Stark are studying Loki's septer

Hulk climbs a building..

Black Widow
Being a Red Room victim, Black Widow is an expert assassin.

Hawkeye
A master archer

Quicksilver
A guy who can run really fast, and takes a bullet for hawkeye

Scarlet Witch
A master of Mind Control

Spiderman (Iron Spider suit)
Stark builds Parker a new suit and makes him an avenger.