Explosive cranial dispersal: 20%
There's a stupid ad for some medical product, which says "In clinical trials, the most common side effect was headache".
A curiously evasive and meaningless statement. The moment I heard it, I immediately realized that the lab results must have looked something like this:
| Side effect | Incidence |
| Headache | 99% |
| Massive brain haemorrhage | 98% |
| Malignant cancer of the genitals | 92% |
| Tertiary syphilis | 85% |
| Windows NT | 76% |
| Smallpox | 40% |
| Death of one kidney | 33% |
| Explosive cranial dispersal | 20% |
| Total body ionization | 11% |
So beware.