Twisted Metal (but didn't think of pre-ordering it ahead of time), good news! Axel was formerly only available as a pre-order bonus, but as of tomorrow, April 18, his vehicle will be available to all. You too can run around on two wheels, pushing smaller vehicles around with your special moves.
The PSBlog has also posted a video, embedded below, of the Sweet Tooth skin going to Starhawk when it launches early next month. Every (new) copy of Twisted Metal has a code for the Outcast skin, so you'll just have to punch that in when the Starhawk comes out.