Infinite Rocket Launcher:
After beating the game, it will be available to buy for 1 million Pesetas.

Mathilda Handgun:
After beating the game, it will be available to buy for 100,000 Pesetas.

Tommy gun with infinite ammo:
Beat the Assignment Ada mini-game to make the "Chicago Typewriter" available to buy for 1 million Pesetas.

Beat El Gigante easily:
Run between his legs when he's close to blast him from behind. When he's coming at you, shotgun blasts to the head work well as you dodge his attacks. After he roars, he'll start to kneel. Get close to him and use the Action command to jump on his back and slash away. Repeat a couple more times, and you're done.

Avoid El Gigante the Second Time Around:
After the raid, you will have to choose a path: either Left or Right. Choose Right and, with the shotgun, make the boulder drop on El Gigante's head. About face and either kick or use the handgun to get through the chained door. You will have to be quick. Go through another one in the same way, and find a key, most likely in one of the last huts down the center.

Make quick cash killing birds:
Toss a Flash Grenade into a bunch of them, to kill them all instantly, making them drop lots of Pesetas. You can also pick them off from a distance with your handgun so as not to alert the whole flock.

5,000 Easy Pesetas:
Look behind every painting of Saddler. Kill One El Gigante Instantly (at the Lava Pits):
When you get to the lava pit, proceed toward the huge double doors. A cut scene will show two El'Gigantes coming. Run to your right and go up the ladder. Wait until one of the two El'Gigante are about to shake the platform. Then take the zipline down to the other side of the arena. Wait untill one of them is standing on the trap door and pull the lever. Now just kill the other one normally. Do not go near the lava pit until it closes or it will grab you.

Get jewels to sell:
In the Village stage, shoot the bird's nests off the trees.

Keep and Sell the "Special" Rocket Launcher:
Get the infinite rocket launcher. Ada will throw you the "Special" Rocket Launcher in your battle with Saddler. Grab it but do not use it. Use the infinite rocket launcher to kill Saddler and when you start a new game, it will be in your inventory to sell.

Scope Ashley:
When Ashley is either up on a ladder or a cliff, you can point your gun at her and she'll call you a pervert while grabbing her skirt. Any ladder where Ashley is too high up, and where you'll have to use your sniper rifle to look up her skirt, she will not notice you and, therefore, will not stop you.