I would look at cards with an annual threshold bonus which you are otherwise unlikely to achieve.
Examples:
JP Morgan Select VISA earns one Ultimate Rewards point per dollar, with a 25,000 point bonus at $100,000. Discussion here:
http://www.flyertalk.com/forum/credi...signature.html
Chase British Airways VISA earns 1.25 points per dollar, with a companion award at $30,000. Make sure you understand the limitations of the companion award before deciding if this has value for you. Primary discussion in the BA forum.