"... but the most remarkable thing of all is: I get paid for doing this."
A vendor was not forthcoming in providing a sample of their TDES DUKPT pinpad; in frustration I said "I can probably just make one with spare parts in my junkbox"; then I did just that. It was later handy in proving bugs in the vendors' product.
Frankencalculator; re-brained HP12-C with crypto functions. Actually, this is incomplete. I got it running as an emulator of other HP calculators in the 10-series, but I got distracted with other projects. I expect to come back to this in 2017.