Air Guitar:
At the main menu press these buttons in quickly: Yellow, Yellow, Blue, Orange, Yellow, Blue.
Eyeball Head Crowd:
At the main menu press in these buttons quickly: Blue, Orange, Yellow, Orange, Yellow, Orange, Blue. This will make everyone's head in the audience turn into a eyeball.
Flaming Head:
At the main menu press in these buttons quickly: Orange, Yellow, Orange, Orange, Yellow, Orange, Yellow, Yellow. This cheat will give your character a head that is on fire.
Horse Head:
At the main menu press in these buttons quickly: Blue, Orange, Orange, Blue, Orange, Orange, Blue, Orange, Orange, Blue. This will give your character a horse head.
Hyper Speed Mode:
At the main menu press in these buttons quickly: Orange, Blue, Orange, Yellow, Orange, Blue, Orange, Yellow.
Make Grim Ripper play Gibson Les Paul:
After unlocking the Grim Ripper, select him as your guitarist in Career mode, then exit Career mode. Next, go to Quick Play mode, choose any song at any difficulty, and either finish the song, or quit once it has started. Then, go back to Career mode, and the Grim Ripper will be playing the Gibson Les Paul with the Cherry Sunburst Classic skin! To make him play the scythe again, simply select it in the "Change Guitar" menu.
Monkey Head Crowd:
At the main menu press these buttons in quickly: Orange, Blue, Yellow, Yellow, Orange, Blue, Yellow, Yellow. This will turn everyone's head in the audience to Monkey Heads.
Performance Mode:
At the main menu press these buttons quickly: Yellow, Yellow, Blue, Yellow, Yellow, Orange, Yellow, Yellow.
Play The Scythe With (Almost) Anyone:
First you must have Grim Ripper unlocked and select him. Then select another character. The character MUST have their other outfit unlocked. They will have the Scythe unless you change the guitar. Note: Since Clive Winston and Xavier Stone do not have an unlockable outfit, they can't play the Scythe.
Unlock Battle Axe:
Successfully complete Expert mode.
Unlock Casket:
Successfully complete Medium mode.
Unlock Eyeball:
Get a five star rank on all songs in Hard mode.
Unlock Fish:
Successfully complete Easy mode.
Unlock Snaketapus:
Successfully complete Hard mode.
Unlock The Log:
Get a five star rank on all songs in Expert mode.
Unlock U.S.A.:
Get a five star rank on all songs in Easy mode.
Unlock Viking:
Get a five star rank on all songs in Medium mode.
Hint - Playing The Ripper's Scythe in Career Mode:
Unverified. First, unlock the Ripper in Career Mode. Switch to to the difficulty you intend to play on, and select your desired guitarist. Switch to a different difficulty and select the Grim Ripper. Now, switch back to the difficulty you intended to play on. The poster should read "your guitarist" playing the "Scythe."
As long as you do not change your guitar or character, your guitarist will be using the Scythe on each song of that difficulty. To return your guitarist to non-lethal guitars, simply change your guitar in the "change guitar" menu.
A similar process can equip the Ripper with a mortal guitar. Move onto your preferred difficulty as the Grim Ripper. Go to any other difficulty, select your desired guitar on any character (besides the Ripper), then return to your preferred difficulty.
Unlockable Co-Op Guitars:
Here is how you can unlock additional Basses in Co-Op mode
Gibson SG Bass - Beat 10 Songs
Gibson Grabber - Beat 20 Songs
Gibson Thunderbird - Beat 30 Songs
Gibson Les Paul and skin - Beat 40 Songs
Hofner Bass - Beat every song
Lava Pearl Musicman Stingray - Get 5 stars on at least 10 songs
Cream SG - Get 5 stars on 20 songs
Natural Sunburst Gibson Thunderbird Bass - Get 5 stars on every co-op mode song
Natural Maple Gibson Grabber Bass - Get 4 stars on all co-op mode songs
Unlock Everything:
Input the following code on your guitar at the title screen: Blue + Yellow + Orange + Red + Orange + Yellow + Red + Yellow + Red + Yellow + Red + Yellow.