First Basemen and Saving Errors
I've run the data for 1st basemen preventing errors, using a similar method as Tom Tango used for shortstops in this year's Hardball Times Annual. I looked at how many throwing errors (retrosheet gives you error type of field, drop, or throw) each infielder made, and how many throws were completed. Then I compare, for each infielder, how the first baseman did compared to how that infielder did with other 1st basemen.
I only looked at years 1985-2007, because I wasn't confidant in the data before that. While retrosheet still gives you error type, there are far fewer throwing errors in the 60's and 70's. Most likely its incomplete data, and errors are considered fielding errors by default if information is not complete.
Todd Helton came out the best, saving an estimated 71 errors, which is worth 57 runs. I used a run value of 0.8 runs per error saved. According to The Book, an error is slightly more harmful than a single, as sometimes the batter gets more than one base.
Others rating very well were Wally Joyner, Travis Lee, Steve Balboni, Pete O'Brien, Keith Hernandez, Richie Sexson, John Olerud, and J.T. Snow. Sexson is not a skilled defensive 1st baseman, but he is the size of an NBA power forward. Seattle infielders faced with a difficult throw can chose to err on the side of throwing it high, knowing that Sexson will come down with the rebound.
Down at the bottom there are people you'd expect, such as Mo Vaughn and Frank Thomas, some that are a little surprising, such as David Segui and Eric Karros, and at the very bottom of the list is a real surprise, Tino Martinez, who was considered a good defender.
Martinez is a fluke. He's -47 errors overall, and -38 of that is from his second basemen. Which second baseman in particular? Chuck Knoblauch. Tino was just unlucky enough to play the position when Knoblauch forgot how to throw.
Data for all 1B with 1000 or more throws received is here.