There is an excellent example in humans.
Sinuses.
For many people, the misery of sinusitis is real. So what’s going on there?
Sinuses are spaces in the bones in the face. They are lined with cells like the “skin” inside your nose. They can get infected and swollen, like when you have a cold/head cold.
Draining properly allows the sinuses to clear infection.
The maxillary sinus drains into the nose.

But where is the drain hole?

Here it is – at the top. The top?
Who puts a drain hole at the top? Not some intelligent designer, that’s for sure.
An operation to solve the problem, antrostomy, involves widening the drain hole so that it drains better.
It’s at the top as we evolved from animals where it was located in a better place – however, evolution doesn’t improve everything – things that don’t affect our success at producing offspring, or don’t make us unattractive to potential mates, don’t tend to have much of an effect on evolution.
I’ll just leave you with this quote, which is extremely insightful:
What rarely seems to be understood about intelligent design is that it is like playing chess against yourself. Every problem that a piece of apparent design gets round brilliantly was itself made by the same designer. Why give a bird a long beak to get into shells for food? Why not just put the food on the outside where the bird can get it more easily? In fact, why make animals need food in the first place?
Inventing problems that you then solve is the opposite of intelligent design. It’s stupid.
Instead of going down the tired old road of explaining what the Theory of Evolution is and what it is not to show you how backwards this question is, I will simply ask you to provide 1 demonstrable, verifiable, falsifiable piece of this evidence that you claim we are totally surrounded by. Please make sure you understand the definition of evidence and that “I cannot think of any other answer so it must be intelligent design”. is not evidence.


As I asked for just one piece of demonstrable, verifiable, falsifiable evidence that supports your claim I am offering two examples that disprove it. These are two different horned animals with a common design flaw. Unchecked, the horns will pierce the skull and slowly but painfully kill the creature. If an Intelligent Designer actually designed this growth pattern of horns for these animals it was not very intelligent.
I await your reply with great interest.
This answer is four years old and I still get theists of all flavors telling me how stupid I am, how uneducated I am, providing me with philosophical arguments instead of objective, verifiable, falsifiable, credible and demonstrative evidence and just being obnoxious and arrogant. For this reason I am shutting down comments. There is nothing new in the comments and I am bored with repeating myself. I appreciate the upvotes.
This answer is generating a whole new batch of upvotes and I have received a few private messages asking me to allow comments again. I will do so but with this warning to Fundamentalists, Homo Trollians and Neandertrolls: I will not respond to any more bullshit comments from any of you. You will not say anything that others haven’t already said in the past 4 years. I will not only BLOCK you but I will delete any comments which are nothing more that personal attacks. If you have objective, verifiable, falsifiable, credible and demonstrative evidence to support your claim in your specific Intelligent Designer/god then provide it, otherwise just move on.