You should always use a condom, unless you've got a really good excuse not to—like you were roller-skating down the street, tripped on the curb, fell into the back of a woman who was bent over packing her car, and accidentally had intercourse with her! That's the message of some amusing new pro-condom cartoons from Grey in Germany for MTV in Switzerland. See three full ads here. Such scenarios, of course, are unlikely—thus, the tagline: "Sex is not an accident. Always use a condom." The campaign is pretty airtight, logically speaking. However, in researching the topic, it becomes clear that many people have asked, in public Internet forums, whether a person can, in fact, have sex accidentally. Usually these questions come from a) young couples who have pledged to be celibate before marriage; and b) male friends who regret that their wrestling in the bathroom went a little too far. In both cases, condoms wouldn't be the worst idea. Via Ads of the World.