I share so that others can learn from it. I had one of those dreaded creaks. It creaked in unison with my cadence. First thoughts - bottom bracket. Removed bb and regreased threads - re-assembled. Creak still there. Disassemble and grease pedals - same creak. Creak would be most noticeable on hard pulls, sprints and climbs.
Solution (in this case). The quick release wasn't tight enough allowing the wheel to move slightly in the drops. I just gave the QR a half turn tighter and the creak went away.
First thing I check next time