There's two types, actually. One is the weapons that Daemons use, the other is a weapon with a Daemon trapped in it, making it more powerful, but the Daemon inside the weapon can corrupt the person using it.

Weapons used by Daemons are generally used by Khorne and Nurgle Daemons, Slaaneshi and Tzeentchian daemons use claws and sorcery respectively, though Greater Daemons all have their own weapons, and some Lesser Daemons that are favoured by their God will have them, too.

As for Daemons themselves, they'll probably be another faction, allied to Chaos. They'd probably be really different to the others, what with being mostly melee, with warp magicks scattered throughout, a whole new meaning to asymmetric. For now, think, which Daemons would fill the Basic slots, Tactical, Assault, Heavy, Ground Assault, Support. Though, they may be Elite units in the Chaos Space Marines.

The weapons with a daemon inside them are Daemon Weapons.
The weapons wielded by daemons don't have a particular name because they don't exist as independent equipment: Rulewise they are part of the daemon itself.

GW split CSMs and Daemons into two separate armies with 4th Edition, and it's good that way: More coherent and easier to balance.

because you start being aggressive with me from the beginning

As a side-note:
1. WH40k is an aggressive game. The baseline aggression is higher.
2. This is a conversation via text-only, which robs us of other means of communication like gestures, mimic and voice-modulation. This means that messages seem more aggressive than they actually are, because deescalating meta-messages are missing.

It is perfectly normal for conversations on such a forum to be perceived as overly aggressive. (Have seen that a dozen times in various forums.)

I'd settle for Chaos Spawn for its neutrality seemingly befitting the undivided chaos of Traitor Marines.
What's special about this unit is it's summoned through a Chaos Marine. Where Orks have Waagh; Chaos Marines could have Chaos Spawn?

well i love chaos spawn so much and i would like to play by him as elite it would be awesome , the question is .... when they will bring it :/