One of my best performing teams, we stopped breaking stories down into tasks because we were able to get them small enough in refinement that they started seeing it as not necessary to spend time doing the task break down. They would plan how they would attack each story at sprint planning and have an idea and then throughout the day communicate on who would work on what. They did a lot of pairing and some mob programming throughout the sprint. We also used a kanban board with stories and not a traditional scrum board because we had no tasks on the board. We also stopped caring about hours burn down and just kept a story burn down as an information radiator. Other than that it was standard scrum ceremonies and roles but that one deviation really worked well for that team.
In our retros we always looked at cycle time and cumulative flow to improve for the next sprint. IMO combining scrum ceremonies, roles and time boxed commitments with kanban based flow and XP practices was highly effective.
Anyway, if you are have used scrum what are the deviations (from OTB scrum) that have worked the best for you?