If your module's/server's players will be using NWNCX, you can create and add brand new weapon visual effects. The default game doesn't allow adding new ones, but NWNCX modifies the game's behavior to open the possibility.
Some example new weapon VFXs made when virusman first added to option.
When adding new VFXs by scripting, you can use the line number from your modified iprp_visualfx.2da (from your hak file) instead of one of the constants used by nwscript.