1. Don't know what it is.
2. Don't have the cash.
3. No one has purchased it for me, yet.
Why don't you just burn me a copy and send it my way? 
Da devil.

It's a MASSIVE open world shooter. You play as a spoiled rich kid vacationing with a bunch of other spoiled rich kids on his parent's money. You skydive onto an island and land in the territory of this crazy pirate. The guy is certifiably insane. He captures you but you manage to escape with the help of your brother (who was killed during the escape).
I love how you start the game as someone who is lost and weak and who freaks out the first time you kill someone...but as the game progresses your character actually begins to ENJOY it and develops a bloodlust.
To be honest I haven't touched much of the main story. The game is absolutely HUGE and there are enough sidequests to keep you playing for a hundred hours.
Leveling your character is fun because there are tons of new abilities and skills you can learn.
The weapons are fantastic. Assault rifles, sniper rifles, SMGs, molotovs, grenades, rocket launchers, a flamethrower, bow, etc. The guns can all be fitted with attachments that you purchase. Optical sights, silencers, etc, etc.
It's a huge sandbox kind of game and there are always enemy strongholds to storm, vehicles to drive, wild animals to kill, herbs to gather, bounties to accept, etc.
Ah, the vehicles! There are jeeps, hang gliders and jet skis. The island is so gigantic that if you didn't have these things it would take forever to travel (though you can travel to outposts you've liberated). Outposts are enemy strongholds that are set up all over the island.
The wild animals! You have to be careful. There are boars, panthers, leopards, etc in the jungle and they're VERY deadly. There are also dear, goats, pigs, wild dogs (also dangerous), sharks, alligators, and more. Killing them will let you skin them. Skinning them will allow you to craft different skins that you can use to hold more ammo, weapons, medicine, or throwable items.
There's much, much more but if you love open world shooters that give you a ton of freedom (and I know you do) you'll love Far Cry 3.