Knees: Why do knees have to bend the way they do, and why are they so out-there and unsupported by something stronger than ligaments? If you go sideways just once, everything stretches out of shape and you're left with a dicky joint forever. Plus each joint has to handle all the weight of the human body on an angle (especially if you're female).
Elbows: Same thing, but with a really limited range of motion. Silly idea.
Temporal Bone: Why such a thin casing over the brain in just a couple of spots? If you're gonna have a solid barrier of bone, make it thick all the way around.
Cervical Spine: "Hey! Let's put an eight-pound lump of bone and meat jello on top of this stack of bones filled with meat jello, and make it really vulnerable to breakage or stretchage!" As an extra added bonus, nothing else in the body will work if you fuck part of this system up.
And we can't turn our heads 270 degrees the way owls can, and we have a bad layout of large vessels in the neck. It's just a fail all the way around.
Urethra, female: Who thought of putting the opening to a system that must remain sterile in the middle of a soup of bacteria, some good, some bad? Who, having done that, would think it wise to make the entrance to that sterile system only a few centimeters long? This is, mind you, without the acidity of the mouth or the protection of mucus to keep bad bugs in check.
Prostate, male: Oh, come *on.* How did "secretory gland inclined to swell and block the flow of urine" get design approval?
Any area through which a nerve has to pass: Let's make it really, *really* small, then add a bunch of stuff around it that's likely to swell and irritate the nerve. Brilliant.
The lack of regenerative capabilities: IKEA could design a better body overall. If something breaks, you just limp on in to the Meat Part Store and buy another bit to screw on with a teeny Allen wrench.
No, I'm not feeling bitter today. Why do you ask?