Devil May Cry

Replay bonus
Finish the game on easy mode. After start a new game.
You will keep all your items and weapons from the previous game.

Easy mode
Finish missions 1, 2, or 3 using at least one continue. At the begining
of the next mission, there will be an option to change the game to
easier. Note: You cannot return to normal mode, if you activated the
easy mode.

Unlock hard mode: Finish the game once
Unlock Legendary Dark Night mode: Finish Hard mode
Unlock Dante Must Die mode: Finish Legendary Dark Night mode
Unlock infinite Demon Form: Defeat Dante Must Die Mode

Good Combo
Press O twice then wait for 1-2 seconds then press it again.
Dante should then do a combo of about 10 hits.

Get Lucia's Extra Outfits
1st Outfit - Finish the game with Lucia
2nd Outfit - Finish the game with Lucia using Hard difficulty
3rd Outfit - Finish the game with Lucia using Must Die difficulty

Get Dante's Extra Outfits
1st Outfit - Finish the game with Dante
2nd Outfit - Finish the game with Dante using Must Die difficulty.

Unlimited Devil Trigger
Press R1, L2, R1, triangle, x, triangle, R2, R3, R3, R1, L1, triangle,
square, square, square, R1, R2.