A poison dart was a dart that was either coated in poison or injected poison upon impact. Poison darts were also known as toxic darts.
Poison darts were preferable over more direct assassination means for several reasons. First, with an appropriate toxin, the victim's death could be nearly-instantaneous, and essentially guaranteed. Secondly, the use of lethal toxins often incapacitated the target before he even realized what was happening, protecting the identity of the attacker and allowing time for escape. Because of these reasons, these exotic weapons were used by various bounty hunters and criminals across the galaxy, most notably Jango Fett and Jodo Kast. The only drawback is that they had a relatively short range.
These weapons are carried by the protagonist Jango Fett throughout the Star Wars: Bounty Hunter game. They are extremely scarce, as he can only carry up to 15 at a time and are hard to resupply. Only extremely large creatures, droids and 'bosses' are immune to the darts.