perquisite

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A payment, profit, or benefit received in addition to a regular wage or salary, especially when due or expected.
• noun Something regarded or claimed as an exclusive right by virtue of one's social position or rank: synonym: right.
• noun A gratuity; a tip.

from The Century Dictionary.

• noun An incidental emolument, profit, gain, or fee, over and above the fixed or settled income, salary, or wages; something received incidentally and in addition to regular wages, salary, fees, etc.
• noun In law, whatever one gets by industry or purchases with his money, as distinguished from things which come to him by descent.
• That may or must be sought out.

from the GNU version of the Collaborative International Dictionary of English.

• noun Something gained from a place or employment over and above the ordinary salary or fixed wages for services rendered; especially, a fee allowed by law to an officer for a specific service.
• noun (Law) Things gotten by a man's own industry, or purchased with his own money, as opposed to things which come to him by descent.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mostly plural Any monetary or other incidental benefit beyond salary.
• noun A gratuity.
• noun A privilege or possession held or claimed exclusively by a certain person, group or class.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an incidental benefit awarded for certain types of employment (especially if it is regarded as a right)
• noun a right reserved exclusively by a particular person or group (especially a hereditary or official right)