Let's face it. Retrospectives can quickly become monotonous. If you don't change it up, the value you get out of it will quickly diminish.
The facilitator role is typically taken on by the ScrumMaster. But in some cases the Coach (if there is one) will get things started and then transition over to the ScrumMaster.
The facilitator has a difficult task because they are trying to keep things fresh so they can maximize the benefit from a Retrospective. But if you're holding a Retrospective every 2 weeks, that's over 20 Retrospectives a year. That requires a lot of creativity from your facilitator.
If you find yourself in this situation, it may be time to bring in a outside facilitator. Many facilitators are reluctant to do this because they see it as a sign of weakness. On the contrary it shows that they're recognizing an area for improvement. It takes courage to take this leap.
Other facilitators feel that bringing in an outside person will alienate the team. But if they themselves feel that the Retrospectives are losing their value then so is the rest of the team. What's the worse that can happen?
One of the best attributes of an outside facilitator is that they are truly unbiased. They don't know a whole lot about the team or the project. This prevents them from trying to steer the conversation in a certain direction.
Sometimes the outside facilitator will lead the team to a path they've already been down. But this actually a good thing. It shows that the team didn't address the issue the last time it was raised and hearing it from a different person may highlight the need to get the issue resolved.
Some teams don't have the luxury of an outside facilitator. If you fall into this category then try to rotate the facilitator responsibility amongst the team. This will allow them to work on their facilitation and speaking abilities. Having the opportunity to do this within a small group can make it feel safe to fail. Also, this generates very different Retrospectives.
Just try it.
Find another facilitator in your organization and agree to run each other's Retrospective.