New to Microsoft Excel? Looking for a tip? How about a tip so mind-blowingly useful as to qualify as a magic trick? You're in luck. In this MS Excel tutorial from ExcelIsFun, the 622nd installment in their series of digital spreadsheet magic tricks, you'll learn about a robust formula for counting unique items in a list using the SUMPRODUCT, COUNTIF and an array formula component. You'll also see an array formula that uses SUM, IF, FREQUENCY, MATCH and ROWS functions to achieve the same.