[ZeLpH_MyStiK]

There seems to be a bug with the tab key, I've tested this on N-Pulse as well as Classic.
If you press and hold S/D (and probably many other keys will work too) and then press and hold the Tab key, it will cause the action that would normally result from the first keypress to repeat over and over again.

Examples:
If you press and hold S and then press and hold the Tab key, your sword (on classic-style servers) will swing repeatedly.
If you press and hold D and then press and hold the Tab key, your npc (on classic-style servers) will be fired repeatedly.