Play a "Connect-Four" style game, earning a game piece each time you answer an estimation question correctly. This game asks the players to estimate the answer to addition, multiplication, and percentage questions. Choose difficulty level, question types, and time limit. Estimator Four is one of the Interactivate assessment games.
Here is a similar interactivity that doesn't have the Connect Four interface.
In this interactivity, you can choose 'Counting' where the students have to estimate the number of stars.
More or Less Estimator
Is the number of objects more or less than the given estimate?