Here is a great online Inference Riddle Game.
To play you simply click on the button on the left side that says Show a Clue. One clue at a time is shown and as soon and you think you know the answer, you type it in the box at the bottom left of the page titled Make a Guess and click OK.
A simple and easy have students practice making inferences. Once they have done all of the riddles, it would be great to have them create their own!