For me, it was when the three rocket boosters landed, almost simultaneously, ready for re-use.

Just tricky cool.

In today's launch, what was tricky cool to me is that it isn't one big LOX engine, anymore. It was like 3 concentic circles of LOX engines, each delivering power (when required), available to deliver more power (when required) etc. Obviously, we couldn't have done 30 LOX engines 30 years ago, but today, we can. Too cool!

-John