As your Achievement percentage increases (by unlocking various features and progressing through them), the additional Crisis Mission categories will be revealed and become available.
Crisis Missions secret weapons
Kill the opponent in brown body armor that appears for a short time in the following levels to unlock the corresponding weapon.
Flame thrower: Drycreek Plaza; in the store room
Gatling gun: Grassmarket Street; in the first open area
Grenade launcher; Belforte Hotel
Laser rifle: Garland Technology Center; the room with the automatic gun turrets
Missile launcher: Garland Park; among the STF trucks.
Double Gun mode
Get over 60% completion to unlock double gun mode in story mode.
Grassmarket District
To unlock the Grassmarket District scenario in story mode, complete the original Garland Square scenario. Grassmaket District is a PlayStation2 exclusive mission that follows events six years after the Garland Square scenario.
Increasing lives and credits
Completion of Story Modes will normally gain you one Life and Credit. This is shown by a screen following completion, indicating what you have gained/unlocked in the game. Note that losing the game by running out of Credits can also gain you a Life/Credit. Note that you can change the number of Credits you start with in addition to Life, in the game settings.
Recommended zone selection order
Generally, the main mission (Garland Square) should adjust difficulty to according to player skill, but if you are new to the game or have not played the arcade version, here is the recommended order in which you should select the zones, with the least challenging first, and most challenging last. This also seems to be the main default order that the game chooses on selection timeout:
Drycreek Plaza (Easy)
Garland Park (Medium)
Garland Technology Center (Hard)
Story Mode Special
Complete both Story Mode scenarios. Story Mode Special allows choice of the machine gun, plus shotgun and handgun, which all can be switched between by pulling the trigger while taking cover.
Tiger and Edge
Consider Tiger and Edge to be the toughest Bosses of the main mission, with the exception of the Geyser 1 battle with Lynch and his collective backup troops. Tiger has brute strength and can soak up lots of bullets, while Edge (formerly known as Edgey in the arcade version) uses acrobatics and speed to dodge shots and catch you off-guard. Get a feel for when Tiger will throw or swing objects in the area at you, and take cover accordingly. However, Edge is a greater threat of the two due to his lightning speed. Very good players can deflect his Naginatas with accurate shots. You shouldn't have to worry about being double teamed, but if given a choice, you should be more cautious of Edge.
Trial mode
Unlock Trial Mode by completing both scenarios in Story Mode Special.
Unlimited ammunition
Get over 100% completion to unlock unlimited ammunition (no reloads) in story mode.
Zone Bosses
Each zone has its own Boss. The following is a list of zones and the Bosses which are featured in each:
Drycreek Plaza: M1 Tank
Garland Park: Hind D
Garland Technology Center: Tiger and Edge (URDA Special Agents)
Geyser 1: Derrick Lynch (URDA Leader)
Grassmarket Street: A-0940
Belforte Hotel: Jared Hunter (New Leader) on Jetpack
Crimson Sea: Jared Hunter (New Leader) on Speedboat
Note: The appearance of Derrick Lynch has changed greatly from the arcade version. He now has darker skin, a different uniform, and looks more menacing. His main weapon has changed in design, but it still fires like his shotgun did in the arcade.