I had the honor to meet Walt a couple of times. First was at a big rocketry event in Virginia back in 2009 - where I was able to get his autograph on a large Saturn 1B model (~ 4 ft. tall) before I flew it (after which it was promptly retired from flight duty).
The second was at a big fund-raising Gala for the Seattle Museum of Flight. The local club had asked me to build some Saturn V and Space Ship One models that they auctioned off as a fund raiser after we had most of the astronauts and other space dignitaries autograph them. Since they didn't want people asking for autographs at the actual Gala, I was invited to a mixer at the Four Seasons the night before where we collected the autographs (truly an amazing night that I'll never forget).
A very friendly, personable fellow who seemed genuinely interested in the models that I'd provided.