Mmm....C0FFEE.

I must just be late to the party, but: I just realized (approximately a decade later than I should) that C0FFEE can be spelled in hex. How have I never seen a code base use this as a 'token word' (albeit with some high-bit junk)? Actually you'd want to pad the low bits to make it odd too.

The most common cookies I've seen in production code are 0BADF00D, DEADBEEF, and FEEDFACE.