Also spotted on a bumper sticker
I ♥ my dog. I had her ♠.
I'm always tempted to read "I ♥ whatever" slogans as "I heart whatever" rather than the (presumably) intended "I love whatever." Since in this example ♠ is clearly meant to be read as "spayed," I'm inclined to read it as "I heart my dog. I had her spayed."
Besides, if you read ♥ as "love" rather than "heart," then the snappier version of this bumper sticker, "I ♠ my dog," could be read as "I dig my dog," which just isn't funny.
Edit: I've since been informed that "I dig my dog," is, in fact, funny. I stand (and laugh) corrected.