Dance Dance Revolution Extreme

Hidden, Sudden, Stealth modes:
Press Left, Up, Right at the song selection screen to cycle through the following options in sequence each time the code is entered: "Hidden", "Sudden", "Stealth", then back to "Visible". "Hidden" makes the arrows fade out before they reach the mark. "Sudden" makes them fade in as they reach the mark. "Stealth" makes the arrows invisible.
Information in this section was contributed by Devvyn.

Little, Solo, Dark modes:
Press Right, Left, Down, Up at the song selection screen to cycle through the following sequence each time the code is entered: "Little", "Solo", "Dark", then back to "Normal". "Little" removes blue and purple arrows. "Solo" uses DDR Solo style arrows. "Dark" removes the alignment arrows.
Information in this section was contributed by Devvyn.

Freeze off:
Press Left, Down, Right at the song selection screen to remove freeze arrows altogether.
Information in this section was contributed by Devvyn.

Boost on:
Press Left, Right, Down, Up at the song selection screen.
Information in this section was contributed by Devvyn.

Switch scroll to reverse:
Press Down, Left, Right, Left, Right at the song selection screen.
Information in this section was contributed by Devvyn.

Reset all special options to normal:
Press Left, Right, Left, Right, Left, Right at the song selection screen.
Information in this section was contributed by Devvyn.

Hidden options:
Hold Start after selecting a song to display a hidden options screen.
Information in this section was contributed by lindsey_41.

Extra stage:
Play in game mode under Heavy or Oni mode. Get an "AA" or "AAA" rank on your last song on the final stage to play the Extra stage.
Information in this section was contributed by lindsey_41.

One More Extra stage:
Finish The Legend Of Max on the Extra stage with an "AA" or "AAA" rank.
Information in this section was contributed by lindsey_41.

Paranoia Survivor MAX:
Get an "AA" rank on all songs from the Paranoia Brothers Oni course in reverse. It will be selectable as your last stage.
Information in this section was contributed by lindsey_41.

Test mode:
Note: This trick requires a machine with the operator menu unlocked. Enter the operator menu. Highlight the "Game Mode" option, then hold down Player 1 Down + Service + Player 1 Start. Select the "Append" option and enter one of the codes that normally entered at the "Test Mode" screen. Then, hold Player 1 Left + Player 1 Right and press Player 1 Start.

Stages 1 to 5:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter JLEDKZT-KOZGDJJ as a code.
Information in this section was contributed by lindsey_41.

Stages 1 to 15:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter PVAGUPM-UALPOEZ as a code.
Information in this section was contributed by lindsey_41.

Stages 1 to 18:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter RVNYIXO-YKAWEM as a code.
Information in this section was contributed by lindsey_41.

Stages 1 to 24:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter SQFRXYY-JSBERAH as a code.
Information in this section was contributed by lindsey_41.

Stages 1 to 27:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter JHEDXF_-ALZSMSH as a code. Note: "_" indicates a space.
Information in this section was contributed by lindsey_41.

Sync, Burning the Floor (momo), Twinbee stages:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter UBNRXAO-UJGPQQI as a code.
Information in this section was contributed by lindsey_41.

Mode unlock:
Note: This trick requires a machine with the operator menu unlocked. Go "Test Mode" at the operator menu and enter BWUVHBK-KVXFXYA as a code. The Legend Of Max, Dance Dance Revolution, Home Version (Nonstop), Look To The Sky (True Colors mix), Dynamite Rave (Down Bird SOTA Mix), Trip Machine, Paranoia, and Paranoia Max Survivors will now be unlocked.
Information in this section was contributed by lindsey_41.

Alternate song sort:
Press Left + Right at the song selection screen to cycle through various sort options.

Hint: Drop Out song variation::
This is a warning for those who enjoy playing the song "Drop Out". There are two versions in the game. In the first version, foot labels for difficulty appear normal. In the other version, on heavy mode it turns purple. This is a slower version. It is different than the normal one, and in some instances harder.
Information in this section was contributed by Zell52.

Glitch: Oni mode:
This trick allows you to take difficulties from one Oni course and put them onto the songs from another. Go from the starting screen to the "Select Oni Course" as fast as possible. Next, find a course with difficulties that you want put onto an adjacent course. Make sure that the cursor is on the one with the difficulties you desire. Wait until time is about to run out, then move to the course with the songs you want. If you timed correctly, the Oni course with the songs you want will have the difficulties from another course. Note: If you try to put non-challenge steps onto a course with a song that has only a challenge step, the game will crash and reboot, which will take about two minutes to do. Doing this at your local arcade is not recommended.
Information in this section was contributed by am3pfreak.