The word two-fer, or more commonly seen as twofer, is often used to describe a situation in which one gets twice what they asked for. If, for example, you're at your local Meijer store and you see that they have packs of underwear on sale, buy one get one free. That, my friend, is a twofer. Or perhaps the whorehouse down the street has a one night deal, two hours for the price of one. That, again, is a twofer.
Twofers are not limited to items or services on sale, oh no. The phrase "two birds with one stone" is a classic example of a twofer. There is also the world of video games, the place where I first became intimately familiar with the concept of a twofer. My first online game was Quake II, and it featured a very unique weapon for the time: the Railgun. The railgun is similar in concept to a sniper rifle in that it shoots a very precise shot and is best used from a distance. It is dissimilar to a sniper rifle in that if you manage to hit a target with the slug, it will continue to travel through said target. This can lead to some very awesome, yet unexpected, situations. Let's say, for example, you are guarding the red team's flag on McKinley Revival. You are hidden behind one of the many crates in your base, just waiting for the blue team to make their move. Then it happens: two blue guys rush in. They bunny hop up the stairs, jump to the flag platform, pick up the flag, and run. Little do they realize that you've seen the entire situation unfold. At this point you step out, take your place on the flag platform and line up your shot. You shoot for the flag carrier, but the bodyguard jumps at just the right moment that he enters your crosshair. You see the smoky blue particles spiral around the gray trail leading right to where the two blue guys were just standing. But instead of our friends we see gibs flying everywhere and the red flag bounces neatly to the ground.
You look up at the death messages:
"Blue1 was railed by you"
"Blue2 was railed by you"
My friend, you just got a twofer. Exhilerating, isn't it?
The Quake series are not the only games in which one can get a twofer. Many modern first person shooter games take place during a famous war of yesteryear (the Battlefield series comes to mind). Explosives such as grenades are featured heavily with rocket launchers and other such weapons also available. With a strategically placed grenade or rocket propelled grenade, you can easily take out two, three, or even four members of the enemy team. While the terms threefer and fourfer aren't quite as popular as twofer, the concept remains the same.
There is no better feeling than getting twice what you were expecting, therefore the next time you take out two guys with one shot, or buy a pack of socks and get a second one free, loudly proclaim "YES, TWOFER" to alert your peers that you have, indeed, just got two for one.