The Matilda is an automatic pistol, while the Infinite Launcher is a well. On play-throughs of the game, you'll be able to buy both the Matilda and the Infinite Launcher from the merchant. If you bothered saving the game after beating Saddler, then you load it from the load menu, you'll be able to start a new game, but will keep all of the weapons and items you had on you at the end of the last one. Enemies will take a fair amount of more damage, so you'll have to go easy on the ammo.
If you want to make a new game after you kill that damn Saddler, you'll be given the option of choosing Professional Mode, which is a more difficult game option, (trust me!).
Leon s kitted out in his S.T.A.R.S.uniform, Ada will wear her Assignment outfit, and Ashley will be sporting the full Britney Spears kit. Complete the game once,and sum new costumes will become available at the beginning of a new game.