Plastic Surgery Nothing says "sorry I ruined you physically" like offering your mom surgical reconstruction. This is a relatively new thing, at least outside of California—plastic surgeons are starting to create package-deals to recreate a woman's body to replicate the state it may have been in before child-bearing. Boob jobs, tummy tucks, even "vaginal rejuvenation," which is just creepy beyond all creepy, especially coming from your kid. Hard and fast rule: no gift you give to your mother should have anything to do with her lady business.
Jewelry made specifically "for moms" I'm talking about charm bracelets with her kids' names, or their birthstones, or little 16-karat-gold-plated cherubs hugging their initials or some such. These are the sorts of things that Moms get, feign pleasure, and then quietly put away. They are not good gifts. To be fair, some Moms might wear these, but if so, they probably live in a trailer, eat a lot of macaroni and cheese with cut-up hot dogs in it, and shop primarily at Wal-Mart. And really, no mom wants to be reminded that they do all that. A corollary: any "fine jewelry" sold at Kmart? Isn't.
Kitchen Appliances It's the cliché, I know, but clichés are clichés for a reason. This happens every year, at any gift-giving occasion. Maybe the family needs a new toaster, but Mom doesn't want one just for her. Keep in mind, too, that this sort of gift doesn't get any better if it's an uncommon tool (a crème brulee torch) or very expensive (a sealed eight-burner stainless Jenn-Air Pro-Style range). They all carry with them the message: "hey, what's to eat?" Of note: cleaning supplies, vacuums, or irons? Worse.
Something You Made! You can safely ignore this entry if you're under twelve (and if you are, I apologize for the bit about "lady business" in #1). Go ahead, kid, and make your Mom a macaroni necklace or something. But seriously, if you're of an age where you have some scratch, spend some on your Mom. Just because you can make a photo mosaic of all the dogs your Mom's ever owned, or go to one of those paint-it-yourself pottery places to customize a ceramic mug that isn't dishwasher safe—doesn't mean you should. If you're in your thirties and still making stuff out of construction paper for your Mom, then you're either one cheap bastard or it's almost time for Jell-o and Gilligan's Island in the Community Room.
Whatever You Get for Your Mother In Law (If Your Mom is Present) Even moms that get along fine with their kids' spouse's parents don't want to be compared to them. If you give a bouquet of flowers in a beautiful vase with a little framed picture of the grandkid to your mother, and then give the exact same thing to her in-law counterpart, then yeah, that's a storm brewing on the Mom horizon, buckaroo. You might as well hand it to her and say "Thanks, Mom, for raising me, but at this point in my life, you're about as significant as this other lady over here. Happy Mother's Day!" -- Teague Bohlen