The KaBar Next Generation Knife is the only melee weapon in Urban Terror (not counting Boots, which are not a selectable weapon). The default mode is slash, requiring point-blank attacks. It can also be thrown by changing the weapon mode (the default key to change weapon modes is N). While holding the knife (or grenades or sidearms), a player can execute a kick.
Knife in Jump ModeEdit
Despite the fact that many jumpers prefer to hold a knife while jumping, there is no advantage to holding a knife in jump mode. There is no weight system in Urban Terror and only a Kevlar Vest affects stamina. It is a small weapon and allows for greater visibility, but you can simply use the command
/toggle cg_drawhands in Console to hide weapons completely.
Changes in 4.2Edit
In 4.2, when a player has thrown all but one knife, the weapon is forced from throw back to slash, preventing the player from disarming themselves completely. In 4.1, it was possible to throw all 5 knives and be left with no weapons at all.
In 4.2, a thrown knife appears to move in a straight line. In 4.1, a thrown knife had a slight arc which made it more difficult to aim and also allowed players to throw them over walls and other obstructions.