Best, Most Agonizing Cliffhanger?

SPOILERS for Suzanne Brockmann's Troubleshooters series:

The cliffhanger that probably had me most on-edge for the next book was in Suzanne Brockmann's Over the Edge, when Sam left Alyssa to marry the woman he'd had a one-night stand with at the beginning of the book, as she was pregnant with his child. I was dying to see Sam/Alyssa get their HEA somehow, someway.

For me the most horrific cliffhanger was in "Changes" by Jim Butcher when the hero freaking died!

Mine has to be Dreamfever, where I thought that Mac might have killed Barrons. I agree with @bungluna, though, that the end of Changes was pretty gnarly also.

Over the Edge was pure torture!
I started Fever series few days after Shadowfever was released, so my agony with that cliffhanger was short.
Most recent cliffhanger that drives me crazy is at the end of Tangle of Need by Nalini Singh. Oh, how I hope next book is about Kaleb....

Dance with Dragons.

You know nothing Jon Snow.

I agree with redheadedjen: definitely "A Dance with Dragons"
Also, "Shadow's Fall" by Dianne Sylvan and "Sins of the Demon" by Diana Rowland had rather nail-bitey cliffhangers at the end.
I am always glad to run across cliffhangers in series that I start reading when they have already all been published; not so much when it might be several months or (in the case of George R.R. Martin) several years to get the payoff!!

Oh yeah, the Brockmann for sure. But the end of the first Cat and Bones book was also a heartbreaker.

The end of Angelfall was pure torture for me. I need to know what happened to Raffe