10:10 - A UK environmental campaign that asks businesses, organizations and individuals to cut their carbon emissions by 10% in the year 2010.
86 - 'Secret' code used by restaurant and bar staff when refusing service or ejecting a customer from the premises, and more recently referring to a menu item not available, which is sometimes a lie to achieve the first meaning. The term has existed since the early 1900s and no-one knows the true derivation, although increasingly daft ones are suggested.
80/20 Rule - The theory that 20% of effort produces 80% of results, and very many similar effects; also known as Pareto Rule or Pareto Principle, after its originator.
72 Rule - More commonly known as the Rule of 72, with variations 69 and 70, these are standard figures used by financial folk in calculating quickly the years required for an investment to double (or to halve) at a given interest rate. Typically 72 is divided by the compound interest rate to give the approximate years. 72 is more popular than 69 or 70 because it is quite reliable and easily divisible quickly by lots of different numbers.
64,000 Dollar / Pound Question - The key or crucial question in a particular issue, deriving from an old US TV game show called Take It or Leave It, in which $64 was the top prize (it was an old old show.) Recently the expression commonly increases the sum to 64-million, to keep pace with inflationary values.