Workplace Safety Games

I have about 100 employees (plant environment) and we are looking for ideas for playing games or ideas for incentives for safety or attendance or just some good fun things to do or games to play to put some fun back into the workplace, ideas can be useful ....

Have prices of games could be gas for a certain period of time. Or groceries for a cetain length of time. Also certificates for restauraunts. Even the certificates for malls would be a good thing.