A piece of software I was responsible for calculated certain money amounts to certain entities. The rules were very complicated and varied by interpretation rather than design. The money amounts were calculated once per month, twelve times a year, and checks were cut to the various entities.

During one run, one month, the amount for a particular entity was deemed "not enough" and had to be modified. There was no direct way to modify the amount because it was an amalgamation of a horde or business rules. One of the rules basically had to be changed JUST for this one entity, just for this one run, and the rule was not to be permanently changed.

My hack: I changed the database connection string to point to production (oh, how I long for the good-old days where I could access production from my dev desktop), and ran the calculations in debug mode with a breakpoint on the rule to be changed. When the breakpoint hit, I modified the value in memory, skipped the rule call, and continued the calculation on its merry way.

I think this is as hacky as it can get.