I like coming up with the system design and the low level pseudo code, but actually translating it to the specific programming language and remembering the exact syntax or whatnot I find pretty uninspiring.
Same with design docs more or less, translating my thoughts into proper and professional English adds a layer I don't really enjoy (since I'm not exactly great at it), or stuff like formatting, generating a nice looking diagram, etc.
Just today I wrote a pretty decent design doc that took me two hours instead of the usual week+ slog/procrastination, and it was actually fairly enjoyable.
