For me
Writers:
Greg Rucka: Lazarus, Old Guard
Scott Snyder: Wytches
Writer and artist:
Sean Gordon Murphy: Tokyo Ghost
Artist:
Kenneth Rocafort: Cyberforce/Hunter-Killer
For me
Writers:
Greg Rucka: Lazarus, Old Guard
Scott Snyder: Wytches
Writer and artist:
Sean Gordon Murphy: Tokyo Ghost
Artist:
Kenneth Rocafort: Cyberforce/Hunter-Killer
I started to make a list, but there is almost no logical end to it. If you simply mean any independent comic written or drawn by anyone who has ever worked at DC, I probably physically have hundreds and hundreds of them. Heck it might be thousands.
Almost every person you could describe as a DC writer or artist has some independent comics in their portfolio. I suppose there might be a very small minority who have only worked at DC or Marvel, but it wouldn’t be many. Most have worked for other companies, either currently, or in their past.