The Gecko is one of the Gears created during the course of the Metal Gear Solid franchise. After the 2009 Big Shell incident, Metal Gear production reached an amazing high and Gears of all types were created. One of the most common types was the Gecko which was narrow enough to make it useful in urban environments. All Geckos are from a line of Gears called UGs or Unmanned Gears. Since the fall of the SOP (Sons of the Patriots), production of these Gears has been drastically reduced or stopped so they are an uncommon sight at this time.
The Gecko will have a few different attacks that you need to be aware of. The first attack is one in which the Gecko lowers his head and charges at you. This attack cannot be parried so you need to try to avoid it. The best method for this is actually to Ninja Run almost directly at it but just off to the side so that you miss. He also has a couple of attacks where he will swing at you with his legs. These definitely CAN be parried and if you're good at parrying then doing so will make this battle a cake walk. Finally, there's an attack where he can hit you with a tendril and try to pull you in but if you rotate the left stick, you can reverse it and stun the Gecko.
After you get some hits in on the Gecko, you should get the chance to either cut up his legs or start a Quick Time Event (QTE) which will result in its destruction.
