Unstoppable

The Unstoppable medal is awarded when any player gets 10 kills in a row as the Juggernaut without dying. It is a gold medal with a Spartan helmet on it. When someone gets this medal the announcer will shout "Unstoppable!" to the player that received this medal.

Trivia

 * Most likely a reference to the Marvel Comics character "The Unstoppable Juggernaut".