I agree that 9s and 1s can be a good couple. I think 1 + 5 works out well, too (I picked a 5). Fives seem like pretty-laid back people for the most parts, as do 9s, so they can help balance out a more engaging type (like 1 or 6, for instance).
I also find that in medical/therapeutic relationships, I get along well with 9s, too. My hypnotherapist is a confirmed 9, and my GP is a suspected 9. I've found that I can work well with both these individuals- they're a better fit for me than many other professionals I've dealt with. Don't know if it's specifically because they're 9s- I think they'd be great people regardless of type- but I do seem to get along very well with most 9s.