If an alien symbiote bonded with your Xbox 360 controller, it would probably look a lot like N-Control's Xbox 360 Avenger controller attachment. It would undoubtedly make a lot of the same promises, too: lightning reflexes, more kills.
By making the X, Y and B buttons instantly accessible to your index fingers, like an extension of your nervous system, the Avenger Xbox 360 controller add-on lets you keep your thumbs glued to the analog sticks. In a shooter like Call of Duty, that doesn't just mean you aim faster, without the micro-interruptions of button smashing: You can go prone, aim, and shoot, all at the same time. It looks scary, but the Avenger's learning curve is surprisingly short. Afterward, you'll see no reason to ever take it off.
The trigger extension doesn't work so perfectly . A lot of shooting games require the triggers to return all the way back to their default position before you squeeze them again to shoot, but if you tighten the Avenger's straps, it keeps them halfway pressed at all times. That's a lot of wasted bullets. There's also no extension for the A button, so your thumb still has to occasionally break away from the analog stick to smash it, jolting the feeling that the controller's truly an extension of your hands.
$50 from N-Control