"sin gun" from Neal Asher's Polity universe. Point it at a person/thing or t it at a pre-determined distance, and zap, a 2 metre wide singularity for 1/100000000 of a second.

makes a real good inside-out face

Weapons I-X.

er, hate to break it to you, but SkyNet has been operations since 1974.
[en.wikipedia.org]

Teleportation devices. Since they tend to kill you then recreate a different you somewhere else.

Even worse than teleportation devices that fail to screen for insects are the ones that fail to check for empty space at the destination.

(Anyone else watch that Earth: Final Conflict? It was on at about 1 am, how could you have missed it?)

Anything with tachyons.

Mass Drivers, used for planetary bombardment. Bablyon 5 and Gundam series well know the devestating, planet destroying power that using these with astriods cause. I want every nation right now to commit to no planetar bombardment.

Total Conversion Beams, ala Larry Niven's Known Space series (a Tnuctipun device that converts whatever matter the beam touches into energy at some significant fraction of efficiency).

@SavannahJack: You are of course referring to the "Wunderland Treaty Maker" used in the last Man-Kzinti War by the Humans with great effect. The Planet "Canyon" is aptly named as a direct result of this weapon.

The smaller version is the Slaver Digging tool.

Its basically a disintegration beam where the one beam suppresses the Positive Charge of the Proton and the other beam suppress the negative charge of the Electron. The result is anything that comes in contact with the beams is reduced to monoatomic dust.

Singuns are good, if too personal. Teleportation based weapons are a bit too like artillery of the future. Total conversion beams and wunderland treaty makers are too 1960s.

Personally I think we should ban anything with the words "coherant gluon emmission" or "vector gauge bosons" on the tin. Being able to dick around with the strong nuclear force a la the McGuffin in Peter F Hamiltons "the nano flower" is probably something we would want to think about first before deployment.

Do we really want the ability to crunch matter into nutronium just by pointing a gun at it?

I personally would enjoy the type of weapon that would allow me to launch a small black hole into the center of your planet or sun. Once fired, all you have to do is sit back and enjoy.

How about berserkers? I'm not too fond of them.

I vote for Laurel K. Hamilton's writing. A harsher weapon you won't find.