the best chain grabber is the dga blowfly. If you compare the outside rim of the blowfly to other putters you can easily tell that it would grip the metal more. I have a hard time controlling it though as you really need to get used to it's feel. Of course it all depends on your own putting style with the angle of release and all that. Guys that like a stiffer putter would really hate the blowfly. I am not saying it is the best putter out there i am just saying that it grabs the chains the best. I have compared the blowfly to all of the other putters listed in this thread and more.
My favorite putter isnt designed to be a putter at all. I recently fond a disc that had nothing on the top of the disc except for "trueline". I didnt know what it was, it looked like a mid-ranger, and at the time me and my putter were not getting along, so I started using it for short approaches and putts, it has singlehandedly reduced my score by 3-4 shots per round. I looked on the back of the disc for patent/manufacture info, after a quick web search, it turns out to be made by wham-o corp, the holder of the original patent for old fashioned Frisbees; apparently they want to break into the folf market. Anyhow, this disc works so well I bought the entire line of wham-o folf disc (4-5 disc), and I am waiting on them in the mail. I have used aviars, rocs, and magnets as putters, and in my opinion, none of them are worth the extra weight or lost space in my bag. Maybe I am being to harsh, the roc is useful for shorter downhill drives, and the soft, rubbery, grippy magnet is useful if you (like i used to) use the overhand putting style. I still think the aviar is a POS though.