I don't know that anyone keeps track of this sort of thing...
There are different ways of measuring efficiency of a catalyst too though; you can look at turnover frequency (number of times the catalyst completes the catalytic process per unit time) or you can look at the turnover number (the number of times which the catalyst can complete the catalytic process before decomposition of the catalyst). One is a kinetic effect while the other is more of an overall ability of the catalyst. The best metal based catalysts I can think of are ruthenium based ones that can give TONs in the millions and rhodium catalysts which can give TONs in the hundreds of thousands. I rarely look at TOF numbers, but I have seen Rh and Au catalysts with TOF as high as 400 TO/hr.
The most efficient catalyst is probably an enzyme though. Enzymes are built to be stable for a long period of time under biological conditions so their theoretical TONs would be astronomical compared to metal catalysts. TOFs are probably better too, but that probably varies a lot too because some biological processes don't need a high TOF, but some others need a very, very high TOF. Some TOFs for enzymes are reported in TO/sec; I have seen as high as 4.2 TO/sec, which translates to over 15000 TO/hr.
There may very well be better ones out there, but I don't read much bio literature so I don't really know.