Here’s a few examples from the IRS of ‘Other Income‘ that should be reported on your form 1040:
Illegal income. Illegal income, such as money from dealing illegal drugs, must be included in your income on Form 1040, line 21, or on Schedule C or Schedule C-EZ (Form 1040) if from your self-employment activity.
Kickbacks. You must include kickbacks, side commissions, push money, or similar payments you receive in your income on Form 1040, line 21, or on Schedule C or Schedule C-EZ (Form 1040) if from your self-employment activity.
Stolen property. If you steal property, you must report its fair market value in your income in the year you steal it unless in the same year, you return it to its rightful owner.
I must make a note of this for my 2005 filing.