My favorite sudoku variation over the last year, which I see far too little of, is Arrow Sudoku. I believe what I like about this type is that there are unknown totals to go along with unknown numbers comprising those totals. Sometimes you cannot identify an exact digit but can say its big or small and even that is enough to slowly narrow down the candidate space. I wrote several Arrow Sudoku for Sudoku Masterpieces - too many actually - and had an extra themed grid that seemed fitting to share here during these summer months. Enjoy.
Rules: Fill in the cells with the digits 1 to 9 so that each digit appears exactly once in each row, column, and bold region. Digits in the circled cells represent the sum of all digits along the path that the arrow travels. Digits can repeat within a sum, but cannot otherwise violate the no repeat rules for a row/column/bold region.