One thing that does it for me is the giraffe. The fossil records show no transitional ancestors. A mutation producing longer legs simultaneously with longer neck (not to mention the complex system of valves necessary for such a long neck) to appear simultaneously is extremely improbable. As for the other animals on the savannah, I find it interesting that the same "natural slection" that dictated a giraffe's neck to grow somehow didn't apply to the others.
Now that I have answered your question, how about answering mine. What specific experiment or observation do you feel supports the ToE?