Don't get me wrong, I know my boys enjoy a stuffed pal when they are feeling down. But they already have enough to fill a swimming pool and they have already long ago chosen their favorite plush friends. The ones given to them when they are sick usually end up shoved under the bed or in the closet as soon as the newness wears off. The ones from gift shops aren't even suitable for playing with, since they have all their costumes and doo-dads glued on and fall apart at the first hard snuggle.
Sick kids are often bored kids. A stuffed animal does little to alleviate the boredom for a bed-ridden child. Send a book, a small laptop play set, a craft kit they can do in bed, or a the tried and true crayons and coloring book. If you just must send a stuffed animal, skip the cheapo get well teddy bear and buy a quality plushie that's meant to be loved and abused. Even better, send one that includes a book or something else to help spur my child's imagination so he can get quality play time from the present.