Variables can be defined in one statement instead of several.

// old & busted
var test = 1;
var test2 = function() { ... };
var test3 = test2(test);

// new hotness
var test = 1,
    test2 = function() { ... },
    test3 = test2(test);

In self-executing functions, variable definition can be skipped all together.

(function(foo, bar) { ... })(1, 2);