The game is fun and silly and the concept(plus the medals, I'm a medal addict) made me stay, but there are a few things you might consider adding/correcting.
One useful function would be a target indicator. The girl more or less targets whatever you're facing, but there are times when she'll throw the shoe in a random direction as if she hadn't locked onto anything. If there was a target indicator, I'd be able to tell if I had someone locked on and I could avoid wasting a car part by missing horribly when I believed I wouldn't.
Something else you may consider adding is the option to switch between items or to decide not to use an item. You're forced to immediately use whatever you pick up when you can keep something(a rocket for example) to use it on a stronger car(like a police car).
There's also the issue with the jumping. Not being able to go backwards is sort of weird. as I instinctively find myself wanting to back out at times. Maybe if you could program that in somehow? I don't know.
Aside from that, the graphics are pretty fluid and the quality isn't TOO bad, but it's not top-notch stuff. Great game though. It's definitely fun. More medals would have been awesome too.