No built in functions such as the ones mentioned, and preferably no quick entropy generating methods that are obvious but that's not as important as not using the built in functions. Another requirement is that each run of the function has to truly be a reshuffle of the array so that it can't be predictable.

It's harder than it sounds, but I also don't expect a perfect answer - generally I just want to see how people think out of thee box to try and solve an odd problem.