You know its GG when...
 

As soon as you hear, "Welcome to Summoners Rift!"
2 Ally champs B-line to mid, <---troll speaks shortly after
Claim that they called mid,
refuse to move,
First blood is given,
Rage,
afk,
And its only 1:03 into the game.

/facepalm

when... Volibear is selected on your team. xD

Your support champ is abandoned to solo a lane vs. two tanky DPS.

When your jungler doesn't take smite because all it does is slow him down -_- or when you first start and 4 people all have smite because they think they can use it on a champion :s

you know its game over when the nexus has 1 health left until then surrender is just an option for weaklings! :D

When evelynn and twitch are instalocked, either of them. and then claim they can win the game.

When you have 2 junglers, one of which is Eve and... wait... Hey I won that! :D

Someone picks Kass in ranked in low elo.

Ranked solo queue....

That happened to me. Sona versus Garen and Kayle with Jungle Udyr coming to gank and no one willing to come help. It was hell, and I lost the tower soon after. I shall curse that leaving Renekton forever!