A horrifying beast. The smallsword, a meter-long, needle-sharp spike with a tiny hand guard, is what the rapier is usually caricatured as: an extremely light and quick blade suitable for the physically weak. It's not, however, for the faint of heart; the overriding sensation of picking up a smallsword is (for the somewhat practiced fencer) that something terrible is going to happen. This is because if you fight with sharp smallswords, something terrible is going to happen. The fatality rate per smallsword duel in 18th-to-mid-19th century France was something like 1.5. That's one and a half participants dead on average, which is another way of saying that it's a pointy version of chicken-racing with no steering wheel. People preferred to be shot at with pistols.
The reason why can be easily gleaned by watching some sport épée fencing, which is a reasonable simulation: épée is short for épée de combat, the Victorian French dueling sword that's pretty much identical to a smallsword. Note how many double hits are scored in these fights, but counted as a point for one fencer because those are the rules. Now imagine each of these hits were inflicted with a sharp spike, and keep in mind that it takes days to die from almost any smallsword wound, so it doesn't really matter who hits first. To some extent this behavior is provoked by the scoring, but smallswords are so hard to parry securely, and so quick, that the same scenario frequently developed in real fights; the horrible truth is that a smallsword is so short, and so fast, that even if it's deflected and the opponent stabbed, he can often still stab you back faster than you can pull your blade out of him. It's a bad situation.