Tanegashima

The Tanegashima was a legendary musket that dated back to the Samurai age of Japan. It was identifiable with a handsome wood finish.

It originated when the Japanese first encountered Europeans via the Dutch and got some Arquebus' from them after landing on Okiwana by mistake (they were originally going to China.).

Metal Gear Solid 4: Guns of the Patriots
Solid Snake can procure this weapon by purchasing it from Drebin either by its full price (1,000,000 DP) or get 50% off during the attack on Outer Haven or on Wednesdays and Sundays. It's overall usefulness was little to none, due to it being antiquated by a significant amount (dating back to the 1500s). However, there is a 1/3 chance that the Tanegashima can create a whirlwind effect that will knock soldiers off their feet by a great distance as well as scatter items across the battlefield.

Metal Gear Solid: Peace Walker
The Militaires Sans Frontieres can develop and procure this weapon. In-game, it is due to procuring an intact Rathalos wing. However, it's more likely that, if they managed to procure and develop the Tanegashima, it was somewhere else outside of Rathalos wing, due to the fallacies of trying to create an arquebus dating back to the 1500s with a handsome wood finish from a fleshy, several hundred pound wing that doesn't have any traces of wood in it. It is useless due to being antiquated. However, it does have a 1/3rd chance of causing a tornado to occur, which results in the soldier by blown away to one of the Militaires Sans Frontieres' helicopters.