"May the random variables be in your favor!"
I think "may the logical uncertainties resolve in your favor" makes a bit more sense, at least if you assume a multiverse/UDT setup where only logical facts determine the value of one's utility function, and "random variables" being favorable/unfavorable is just an illusion where copies of you at different locations in the multiverse experience different inputs.
Ah, right. I think a nonrandom variable situation actually came up and I said "May the unknown variables be in your favor" or "May the hidden variables be in your favor".
Is there any rationalist equivalent of "good luck"? I've tried a few variants, such as "work well", "knock them dead", "we're with you" and certain situation-specific phrasings, but haven't found anything that worked generally - though a hearty "may all the gods of Olympus be with you!" can serve. Not a vitally important point, but it would be nice to have something similarly supportive and yet accurate to say.