I've always thought 37 was a popular number for major league baseball pitchers, but finally, thanks to Milt Epstein, I have some evidence. He collected data from Usenet on the jersey numbers of MLBers, and wrote a script to do some stats on the pitchers' numbers. Here is the top portion of the list:
Of 366 pitchers on 28 teams:
Number Count Percent [sic]
41 16 0.0437158469945355
40 14 0.0382513661202186
49 13 0.0355191256830601
43 13 0.0355191256830601
33 12 0.0327868852459016
31 12 0.0327868852459016
32 12 0.0327868852459016
50 12 0.0327868852459016
52 12 0.0327868852459016
51 11 0.0300546448087432
46 11 0.0300546448087432
36 11 0.0300546448087432
35 11 0.0300546448087432
47 10 0.0273224043715847
38 10 0.0273224043715847
27 10 0.0273224043715847
45 10 0.0273224043715847
42 9 0.0245901639344262
37 9 0.0245901639344262 <--------
39 8 0.0218579234972678
48 8 0.0218579234972678
...
So 37 did not fare quite as well as I had hoped it would, but we are still able to make a couple of broad statements: 37 is more popular than average. And (interestingly) about 1 of every 37 pitchers wear the number 37.