The Texas Instrument TI320C40 digital signal processor had even weirder pipeline issues:

- Branch delay slots (https://en.wikipedia.org/wiki/Delay_slot), where one or more instruction(s) after a branch would be executed before the branch actually occurred.

- Load delay slots, where values stored into registers weren't guaranteed to appear until some later instruction. I believe the the value in the register was undefined for several cycles?

Writing tightly-optimized assembly code for these chips was pretty horrible, sort of like playing an unusually tasteless Zachtronics clone.