Can you use any headset that has a 2.5mm connector? or does it need a special one branded for the 360?

Any of those function fine (they're usually found with the cordless telephone accessories in stores). You'll probably want to find one with volume, mute, and microphone volume controls.

i got a 10 dollar one from cvs and it works, but I cause echo I guess because everyone yells at me when I come in. This is when I plug in the smack talker and give em hell right back! :)

i use a military grade ICOM HS-95 headset, it rocks.