The number 42 appears so often in sample Python code that I am now reading the Hitchhiker's Guide to the Universe, despite myself. I see that I must fully understand the context of this inane meme.
Because of the lingering effects of a childhood interest in numerology and Dr. Matrix, I tend to use 137 (Arthur Eddington's "fine structure" constant* when a dummy integer is needed.
I put the book aside after getting through a little more than the first six chapters. It seems to me a painful knock-off of Vonnegut's Sirens of Titan, with coarser humor.
I am glad to have read far enough to learn the origin of the name Babel fish, which was the name of a translation website earlier in the history of the Internet. I also looked ahead in the book and found the many references to forty-two. I do not feel inspired to use the number in my code, though.
* See http://scienceworld.wolfram.com/physics/FineStructureConstant.html:
A dimensionless number that appears in the analysis of quantum electrodynamical Feynman diagrams. It is not currently known if it can be derived from first principals in terms of mathematical constants, but it can be determined as a conglomeration of the electron charge e, ℏ (h-bar), and the speed of light c. In his later years, the English physicist Arthur Eddington concocted pseudoscientific "proofs" on "physical" grounds that the fine structure constant was exactly 1/136. When experiments yielded a more accurate value, Eddington produced another proof "proving" that α ≣ 1/137.