Well, I might personally not have anything that can be affected by a productivity killer, but here’s one for those of you that can: Web Sudoku.
For those of you not familiar with Sudoku, let me explain the game. You have a 9 by 9 grid that is to be filled up with numbers. Each row and column must contain the numbers 1 through 9 (in any order). To make the game more challenging, the grid is broken up into nine 3 by 3 grids. Within each of those grids you must also have the numbers 1 through 9. This will affect how you can place numbers into the respective rows/columns.
When you complete a game, click on the “How am I doing?” button. It will submit the game if it was completed successfully, or show you any errors. You can also hit that button when you are not done to get hints. It will either point out errors that specifically broke the rules above, or it will tell you how many numbers you have in the wrong place but are not yet breaking any rules (because you have not yet finished off a row or column yet). Upon completion, you will be given your time and they will show you a graph of completed games. If you did not need any assistance, the game will show you your rank in the graph!
For the math nerds who are curious, it appears that the game of Sudoku has a skewed right χ2 distribution. What annoys me, is they only seem to have a graph of all games completed. They don’t have a graph that filters out the results from games that required assistance in order to be completed, so those that didn’t need assistance are more likely to be above the curve. 🙁