Gifts for Employees: are they taxable?

Generally speaking, you must include the fair market value of any gifts or prizes you give your employees as wages, subject to all the usual taxes. There are exceptions though.
De Minimis Gifts - non-cash gifts such as food, event tickets, etc. are "de minimis" (to small to bother with) and not subject to tax as long as they are given infrequently and have nominal value.
Cash - cash and "cash-in-kind" (e.g. gift certificates), regardless of amount, are always taxable as wages.
Parties - company parties are not taxable to the employee. For the business, the cost of an infrequent party which serves to promote employee efficiency or goodwill is fully deductible (not subject to the 50% business meals limitation).