[Aetae]

var arr = [1,2,3,4,5], i = arr.length;

while (arr[--i]++);

alert(arr);

Точняк.))

...а, хотя не, не катит :

var arr = [1,2,3,4,5,0], i = arr.length;

while (arr[--i]++);

alert(arr);