Felted cat toys are good. as are sewn ones with catnip inside (provided you're making something for a cat, of course

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not something you make, but one of those small laser pointers. can pick them up cheap and cats LOVE to play with the red dot. some dogs can see it and go nuts over it too. If you make a ribbon to carry it with.....
the crocheted/knitted sweaters seem to always go over well with folks.. If the person is a bit, er, hmmm...how to put this....overly cutesy with the animal ("Oh, that's mommy's little darling! Isn't she sweetsy weetsy...") a cute hat or cape for the animal...something they can dress them up in.
a placemat with a rim for the water/food bowls...something that's personalized. Maybe take a regular plastic placemat, stencil doggy's name on it, glue a rim to it.
oh. LEASHES. I have a dear friend who does inkle weaving. (VERY strong narrow bands, whatever length you want to do) She does leashes/collars for folks in matching colors. weave a strap, sew a snap to one end, and loop the other end for a handhold.
back to the hat/cape thing....I've recently seen some hats made of feathers and jewels. (Yah...over the top, but kinda cute) Some attach to the collar, some are made for poodles...to go in the topknot. They look like something a Las Vegas show girl would wear.
oh yeah...believe it or not....beaded hair extensions. now....with these last two we're talking about high end pooches...but still.
floor pillows. soft, not overstuffed, washable, something the dog can scratch at and fluff up. possibly filled partly with cedar chips for odor control....altho then it shouldn't be washed.....sigh.
the little bags of homemade doggie treats are REALLY well received around here.
OH!! thought of something else. a doggie blanket for in the car. keeps the pooch from scratching the seats, can be washed easily, keeps doggie warm in a cold car. I made a couple using fleece, attached elastic to them so it could be caught under the seat and the fleece would stay put.