I fucking hate Leech Hunter and I want it and whoever came up with it to die and spend eternity being feasted upon by leeches. With that aside, Leech Hunter is a rather hellish mini-game where you have to collect Leech Charms, like the ones found in the Laboratory in the main game. There are 100 in all strewn throughout the Training Facility and you can hold them in sets of ten, fifty for each character. Once you pick one up you can't drop it so you have to manage your space and the enemies properly. I'm not going to give you a list of locations for the leeches because there are some that tend to move about. I will, however, give you the low down on the prizes, the weapon locations and the means of getting every single charm.
Ok the prize system is part of what makes this game a living hell. There are various prizes for the amounts you collect but unfortunately if you were to collect all 100 you would only get the prize of a perfect completion. So to get the prize you have to meet the criteria and not go above it. The prizes are as follows:
0-29: Submachine Gun ammo clip in Rebecca's inventory upon start of the game.
30-59: Infinite Handgun ammo.
60-89: Infinite Hunting Gun Ammo.
90-99: The Magnum Revolver can be found in the room next to the Save Room on the Train.
100: All weapons have infinite ammo.
Now, the means of getting these prizes are what makes the game annoying. Before anything we have to go through the basics. The first thing you need to know is the costumes you pick will have an effect upon what the strongest weapon you find will be. Dressing with Billy in the Jacket and Rebecca in the Leather will net you a Magnum. Having Billy in his normal clothes or Jacket and Rebecca in the Cowgirl outfit will net you the Submachine Gun. Now, the important weapons are as follows: First off you'll find a Shotgun in the sewers before the train crash area in the water, hidden next to the ammo box poking above the water. Secondly the Magnum or Submachine gun can be found in the room in the basement where Billy sends Rebecca through the vents before the two of you get split up. There's also a Grenade Launcher in the basement room with the 'waterfall'. Before you start collecting charms clear the place of all monsters. Save the Shotgun for the Hunters and the Grenade Launcher for the Leech Zombies. The Magnum should be saved for when you start collecting charms as enemies regenerate in the kitchen and a couple rooms in the basement. So be very, very careful with your Magnum ammo. Now, the most important thing you remember is this: the Kitchen contains more charms then you thought. At the back of the kitchen is a pair of sinks, and in each sink is a charm. You can't see them but they're there. If you remember this then getting 100 will be a piece of cake. And finally, a character dieing means you no longer can count their charms. So keep both characters alive. Thats about all there is to it.