Wall Street Fair Share Act - Amends the Internal Revenue Code to impose an excise tax on securities trading facilities, brokers, and purchasers for certain securities transactions. Sets such tax at .25% of the fair market value of the security traded. Defines "security" to include stock in a corporation, partnership interests, debt instruments, or interests in certain derivative financial instruments. Exempts from such tax an initial issue of securities, transactions in certain retirement, education, and health savings accounts, and transactions in mutual funds. Allows the purchaser of securities a credit against the excise tax for the lesser of the tax incurred or $250 ($500 for married couples filing joint tax returns). Requires withholding of excise tax amounts by the transferor of securities subject to the tax.