There is a variation of the left hand low style that I have been using for 7+ years, and it has worked wonderfully for me. A few years ago I noticed Vijay Singh using it on the tour during his win at the Masters. In my second round using it I shot 64 and had 22 putts.
Here's how to do it:
Place your right hand on the top of the grip, like in the normal left hand low grip. Now extend your right index finger down the right side of the shaft. Take your left hand and wrap it around your right index finger and around the grip like normal. Both thumbs should be pointing down the shaft like normal. If it hurts because your finger is not flexible enough, you can move your right index finger slightly under the grip more. Your left hand will "lock" the right hand in place and prevent your wrists from hinging during the stroke.
This grip should feel very solid and stable, and really helps eliminate wrist motion and enables both hands to work together. It's very hard for one hand to take over the other during the stroke, and it has helped me become a much more consistent putter. Try it!
In my Callaway Staff bag:
Driver:Callaway Fusion FT-3 Tour 8.5 Driver (Aldila NVS 75 X Flex)
3Wood:Callaway Fusion 3 Wood (Aldila NVS 75 X Flex)
5Wood:Royal Saber Custom Made w/ Infiniti Shaft
Irons: Titleist 503h 19 degree 2 Iron (TT X-100)
Irons:MacGregor V-Foil 1025 MB blades, 4-PW (TT X-100)
Wedge:Titleist Vokey Prototype 56 degree SW
Wedge:Callaway Forged+ 60 degree LW
Putter:Odyssey White Hot #6
Ball:Callaway HX Tour 56
