I recommend the Sun Ray inline probe. I have one on each of my detectors that can use them.
People claim they add weight, which is true, but it's only 10 ounces for the entire unit. If weight is that important, you can still carry the probe in your pouch while you are swinging. I know one guy that hunts with the detector in his right hand and the Sun Ray probe in his left. That way it's always at the ready.
The Sun Ray inline uses a toggle switch so that the probe is using the same settings as your detector, so you can either use it in discriminate or all metal modes. Also, the sound comes over your headphones/speaker.
No batteries to buy, since it's powered just like your search coil, and no, it doesn't use any extra power, since your detector is either using the search coil or the probe, but not both at the same time.
I have purchased a Garrett Pro-pointer to use with my TDI, but haven't been home to open the package yet. However, I just finished reading a thread on another forum of unhappy Pro-pointer owners. Apparently there is a high failure rate of the switch. However, just like White's with the Bull's Eye II, they are replacing bad units with new ones regardless of warranty.