Start the game with

 maxpayne2.exe -developer

 then press [~] to open the console.

 Now you can type in:

 clear                  - Clear console screen
 clr                    - Clear console screen
 coder                  - God mode, all weapons, health, inifinite ammo
 god                    - God mode
 mortal                 - Disable god mode
 getallweapons          - Get all weapons
 quit                   - Quit game
 showfps                - Show fps rate
 showextendedfps        - Show extended fps rate
 getberetta             - Get Beretta with 1000 ammo
 getbullettime          - Put player into bullettime
 getcoltcommando        - Get coltcommando with 1000 ammo
 getdeserteagle         - Get Desert Eagle with 1000 ammo
 getdragunov            - Get Dragunov with 1000 ammo
 getgraphicsnovelpart1  - Fill in part of the story line
 getgraphicsnovelpart2  - Fill in part of the story line
 getgraphicsnovelpart3  - Fill in part of the story line
 gethealth 1000         - Get 1000 health
 getingram              - Get Ingram with 1000 ammo
 getkalashnikov         - Get Kalashnikov with 1000 ammo
 getmolotov             - Get Molotov cocktail with 1000 ammo
 getmp5                 - Get MP5 with 1000 ammo
 getpainkillers         - Get 1000 painkillers
 getpumpshotgun         - Get pumpshotgun with 1000 ammo
 getsawedshotgun        - Get sawed-off shotgun with 1000 ammo
 getsniper              - Get sniper gun with 1000 ammo
 getstriker             - Get striker gun with 1000 ammo
 jump10                 - Jump 10 high
 jump20                 - Jump 20 high
 jump30                 - Jump 30 high
 showhud                - Turn on HUD
 help                   - Much more debug commands