Recharge your Optus Pre-Paid service online once a month, and you will receive a free game or song. The offer is only available if you pay using a credit card, Visa / Mastercard debit card or PayPal. There are no games available for iPhones, tablets or Windows Phone 7 devices. Optus chooses whether to offer you a game or a song, and you get to choose from a selection (I cannot find a list). Judging by the picture on the website, games include Need For Speed Shift, EA Cricket, The Sims 3, Tetris 2012 and Monopoly. You are given the option to send the content to a friend, if you do not want it.
Compatible devices for games: http://www.optusgames.com.au/devicecheck
Yeah I got one of those when I loaded my initial credit. You get a rap song or something like that. Not worth the bother in my opinion, however I got bonus credit for recharging online compared to buying a voucher at a shop.