Fluffy car mats? I doubt it. Jewellery? Not likely. If you live in America, apparently it's a car. Yes, for the last couple of weeks, the car companies have been touting the valentine's day events - give your loved one a Mercedes, or a Lexus. That's not really a gift is it? It's more of a statement of how outrageously wealthy and/or materialistic you are. There's no real thought goes into buying your wife a car.
Here's my suggestion : grab her some roses on the way home, and a nice box of chocolates. Cook her dinner, take her out to the theatre or a movie. These are all better ways of demonstrating your affection than saying "honey, check out the blown head, dual overhead cams and six pot Brembo's on this little beauty!"
Unless your wife is a gearhead, in which case, go crazy.
Happy Valentine's day :-)