While you can sell most things on eBay, quite a few things are banned. If you try to sell any of these things then eBay will remove your auction and all bids will be void.
Here is eBay's full list of prohibited or questionable items:
Academic Software
Airline and Transit Related Items
Alcohol (also see Wine)
Animals and Wildlife Products
Anti-circumvention Policy
Artifacts
Authenticity Disclaimers
Autographed Items
Batteries
Beta Software
Bootleg Recordings
Brand Name Misuse
Catalog Sales
Catalytic Converters and Test Pipes
Celebrity Material
Charity or Fundraising Listings
Comparison Policy
Compilation and Informational Media
Contracts and Tickets
Counterfeit Currency and Stamps
Counterfeit Items
Credit Cards
Downloadable Media
Drugs & Drug Paraphernalia
Electronics Equipment
Embargoed Goods and Prohibited Countries
Encouraging Infringement Policy
Event Tickets
Faces, Names and Signatures
Firearms, Ammunition, Replicas, and Militaria
Fireworks
Food
Freon and Other Refrigerants
Gift Cards
Government IDs and Licenses
Hazardous, Restricted, and Perishable Items
Human Parts and Remains
Importation of Goods into the United States
International Trading - Buyers
International Trading - Sellers
Lockpicking Devices
Lottery Tickets
Mailing Lists and Personal Information
Manufacturers' Coupons
Mature Audiences
Medical Devices
Misleading Titles
Mod Chips, Game Enhancers, and Boot Discs
Movie Prints
Multi-level Marketing, Pyramid and Matrix Programs
OEM Software
Offensive Material
Pesticides
Plants and Seeds
Police-Related Items
Political Memorabilia
Postage Meters
Pre-Sale Listings
Prescription Drugs and Devices
Promotional Items
Real Estate
Recalled Items
