I spent some time in a muffler shop the other day, Rick. My recommendation is that you get her one of those big mufflers the kids are putting on the back of their cars now. There was a kid there getting one installed and he looked like he was gonna go off in his pants, so it must be the best gift ever. ;-)
Okay, I suck at buying gifts. I've managed to stay married for fifteen years though, so try this: Sit back in your chair, take a long sip of beer, and try to remember something she was looking at in a shop or something she said she liked.