Tekken 5

Get 50 wins in vs mode, then press RP to select the character.

When playing in the Secret Garden stage, your controller will stop working and you cannot control your character. It happens for a minute when the battle starts. You will notice it when the background music starts fading and then stops.

Beat Devil Within once to unlock the stage select feature.

Using any character complete Story mode to unlock Theater mode. When this mode has been unlocked you will be able to view the movies for that character, watch E3/TGS trailers and listen to stage soundtracks.

Beat Story Mode with every character (including Eddy Gordo, Christie Monteiro's extra costume) to unlock 'Starblade' as a selectable game in Tekken 5's 'Arcade History' mode. It appears farthest right (after Tekken 3).

You can unlock Devil Jin by either completing the 'Devil Within' side game or playing a bunch of games in Arcade Mode, VS Mode or Story Mode. 200 or so games in Arcade Mode seems to unlock him after you have unlocked all the other characters.

Eddy is an extra outfit you buy for Christie (500,000G on console instead of the 400,000G price tag on the arcade version).