TR2 Temple of Xian Weapon Combining Bug

Drop a flare underwater, pick it up (Action) and select the harpoon gun a split second later. If the timing is right, Lara will be holding the flare in her left hand and the harpoon gun in her right. Exit the water enough so you can draw another two-handed weapon. Then Lara will fire the ammo of the second weapon at harpoon gun rates, until you run out if ammo. In this case, I press "7" to select the grenade launcher (I'm on a PC, of course). You can also pick up an underwater item to do this, but you must wait longer to select the harpoon gun.