There are many games that support PlayStation Move compatibility, and if you're a shooter fan, you'll want the Sharp Shooter accessory, too.
But maybe that endeavor has been a touch too pricey. If that's the case, you should take advantage of this week's sale at GameStop, where they're offering 50% off on Sony's motion-sensing device and the almost necessary peripheral for FPSs.
For this week only, you can grab the Move controller for $24.99 instead of $49.99, and the Move Sharp Shooter for $19.99, half the cost of its standard $39.99 price tag. Also, to round out the combination, you can nab the Navigation controller from Amazon for $14.99, another $50% off sale (it normally costs $29.99). If you're in the market for a PS3, remember that the standard 160GB machine has dropped in price to $249.99, while the 320GB console is $349.99.
Personally, I haven't used the Move controller for much besides reviews. But maybe that'll change some time soon. I've got Child of Eden here; that ought to be intriguing.