I came across this piece while sorting:
It appears to be similar to 2569, but it's clearly a different part. 2569 doesn't have the ridges and has a spherical tip rather than the cylindrical one on this part. The parts are roughly the same length.
I didn't see the word LEGO anywhere on the part, so I strongly suspect this is from a knockoff brand, but I wanted to make sure before I remove it.
I've never seen that part until now, and it's certainly not in the antenna or bar bricklink categories. I'm fairly confident it's not LEGO.
However, it would be far more interesting to know what it is, but that's not easy to search. A few Mega Bloks parts have been catalogued, but your part isn't there either (I could only check categories bar, weapon and tool/gear before I got sick, though). Considering that database is far from complete, it doesn't mean it's not Mega Bloks, though.
Actually, I think there's a good chance it IS Mega Blocks: the antennas on the Repzyllian Trekker and the Gyro Fighter look very much like yours.
I have one and it is Mega Bloks. You can clearly tell the difference as Mega Bloks always appear lesser quality with slight ridge markings. I got mine from a bundle including Lego, Mega Bloks and COBI. But as Mega Bloks has very limited search facility there are no catalogue numbers
