Mono weapons are edged weapons, that are so sharp their cutting edge is only one molecule across. Whether or not this is accurate or not is open for debate, but they can cut through just about anything like it was melted butter.
Most Mono Weapons are things like knives or swords, distinguished from the run of the mill knife/sword by the term mono being added in front of it. Mono-knife, for example.
Mono-Wire is especially deadly, and care must be taken while handling it. It is simply a wire with a mono cutting edge all the way around. It can be strung between two points, and because it is so thin, no one will see it until they have already been cut. It can be used as a melee weapon as well, but it normally has handles on either end with the cutting wire in the middle.
Mono-wire can also be used as a ship to ship weapon.
[Ship use is in Sol Bianca series.]
Energy blades are melee weapons that are made up of destructive energy. Possibly they are plasma blades caused by the constant atomization of lasers on a forcefield. Whatever they are, they can cut through just about anything, except for another energy blade. They also take a lot of power to use, and must be turned off when not in use.
These blades can take any simple shape, if an ax, sword, shield, or if really fancy, a ball and chain. While these shapes are normally pre-determined, the operator sometimes has the ability to change the shape or his energy blade.
[Light sabers in Star Wars, size/shape change in Splinter of the Minds Eye; Beam Sabers in the Gundam series;
also used in occasional Transformers episodes.]
Grappling hooks are very simple, they are hooks, or some other heavy object at the end of a chain or rope. They are very useful for grabbing on to things, or for throwing from a boat to act as a break.
They are also effective weapons if thrown or shot at something.
[Yamato/Star Blazers.]
Vibro-Weapons are also primarily melee weapons, usually in the form of knives, swords, or maybe a whip. While their blades are sharp, they cause abnormally high levels of damage because they vibrate at intense speeds, making the basic knife the equivalent of a chainsaw.