Does anyone have a list of all the weapons you can create? I have some schematics but cant seem to access them on the workbench.. im a little confused?

I would say look it up at http://fallout.wikia.com/

Same Issue,
Ie Schematics: Billboard
In inventory but I cant build it at benches?

Picked up the schematics for the rock-it launcher and apperently it was deleted from the games files or some junk like that. :/

http://fallout.wikia.com/wiki/Schematics_-_Billboard

I'm fairly certain you can still build it.

The Billboard schematic though is a dummy schematic, not sure to what purpose.

Here's the full list:

http://fallout.wikia.com/wiki/Fallout:_New_Vegas_crafting

Each item has it's own set of Skill point requirements like Survival, Science, Repair or Explosives so if you have all the required items, and it's still grayed out you skill may be too low...