Interesting Question

I forgot to add, this is just for a single sprint; not asking which to get rid of in its entirety. 

Given that the rules of Scrum are no longer being observed, might it be wise to cancel the Sprint event itself?

Ian, if we are honest, not every company fully adheres to Scrum. There have been times when I've been forced to cancel a meeting and I had no say. I can't just say "Let's go ahead and cancel the entire sprint because we can't do our Review (for example)." 

It's simply a question to get people thinking what you would do if you were in a similar situation, and you had to choose between the Review, Retro, and Planning to cancel for a single sprint.

I would cancel the Retrospective..  the plan, sprint &  review are the main events keep up velocity on increments of the product.

The Retrospective,  helps to improve the product build processes.   If we are late by 2 wks on refactoring.. we will still be on same velocity  and Quality. Juggling event  in real time is tricky. the focus  is build increments.

Given the "hypothetical" situation proposed by Curtis, my thoughts are as follows:

All three Scrum Ceremonies mentioned (Review, Retrospective, Planning) are critical collaborative and empirical events in Scrum.   It is hard to choose a "least important" of the three, and yet that is somewhat similar to what we ask Product Owners to do. 

A common practice to help with prioritization is to ask a PO which item they would most prefer to see crash in production, given the choice.   Often, the item they choose has the lowest priority.   I see this as a similar exercise.

That said, I cannot see doing without Sprint Planning, as that defines so much of what the next sprint entails.   I also think it is extremely unwise to go without the Sprint Retrospective, as it is a key reflection point to inspect and adapt how the Scrum Team is working.

Therefore, my answer would be the Sprint Review as the ceremony I would cancel if needed.   I also choose this event because I would have an expectation of the PO and the team working closely throughout the sprint, and the PO effectively signing off (meet DoD) on any items to be presented in a Sprint Review.

It's not a good question. It unnecessarily implies or generates discussion leading to implications that one event is less valuable than the others.  The only reason you might need to cancel one of those events is because of abnormal circumstances... in which case, it solely depends on the situation, but would not be down to one event being less valuable than the others.

I would attempt to reschedule any event that had to be cancelled - are we accountable or not?  Otherwise I'm on the same page as Ian.

Churtis, I hope the "interesting question for thought" you propose is meant purely academic. In that case a lenghy discussion can take place, for example "if it is the first Sprint I find the retrospective more important that after the 20est or so Sprint that went very smoothly".

In the real world, outside the ivory tower, I find all of the meetings important and valuable. Their length might vary greatly though, depending on how the Sprint went. Try to make all of them happen. Otherwise reflect what the impact is of cancelling event x. Dropping the Sprint Review for example would leave the "releasable Increment" "not releaseable" as there was no inspection of the Incement ...

This is absolutely purely academic. I am in an environment where I am implementing Scrum and still dealing with leadership that doesn't see the benefit fully and they have been doing Waterfall for 30 years; they don't change easily. So I've been forced to cancel meetings because management will not allow the dev team the time for the events. This kind of scenario is not common with companies that have adopted Scrum fully, but for the multitude of companies that are in between Kanban and Scrum or Waterfall and Scrum, for example, this is not uncommon. 

When I have been told to cancel the event, I have fought hard against it but I can only do so much and still have a job. I have chosen the Retrospective as the event to cancel because in my company, the Planning and Review are absolutely vital; no release will happen without these. So what I've done is had a shortened Retro where I bring in lunch for the team on the day would have had the retro and it's during our lunch hour. It's tough, but we still get to at least discuss a few things even though it's not ideal. 

Fun question Curtis! 

Although, in my opinion, the retrospective it's the most important one I would cancel it. Depending on the maturity of the team the retrospective will have less and less positive effects. If you observe, you'll see that the first retrospectives will score hughe improvement after that it tends to slow down, cause the team are closer toward their maximum efficiency. 

I know it's not ideal, but don't take it too serious, it's just a hypothetical scenário..

All meetings are important but if I had to cancel one of them I'd look into this specific situation and make a decision. I'd not cancel a planning meeting, in this case the coming sprint might be ruined. Then my choice would be between review and retrospective meetings. If the review meeting is attended by the scrum team and stakeholders and there is some stuff to demo then I'd keep it and cancel retrospective. In this case the retrospective can be done later after the sprint starts. If there is not much stuff to review then I'd move the demo part to the next review meeting and keep the retrospective.

Why cancel a meeting? If the management asks to have less time spent on meetings, you can just shorten all of them. In this way, you save all the ceremonies.

Just my 2 cents

To me that'd be like going through the wilds choosing between leaving behind the map, the phone or the compass, just for the sake of making it more 'interesting' :) 

I already had this situation due to a corporative meeting scheduled last minute where pretty much the whole company got summoned. We ended up doing only the sprint review inside the sprint timebox and arranged the retrospective for the first day of the next sprint timebox, right before the planning. Not ideal but it was the lesser of the evils.

Important thing it was the team that decided for that, instead of staying extra time on a Friday.