I've been a fan of the Vampire mockumentary What We Do In the Shadows for a long time, starting with getting to see a screening of the film at SXSW five years ago.
There are so many brands that do amazing activations at SXSW each year - for example, HBO's Game of Thrones has consistently been an all-star, and this year was no different with the "Bleed for the Throne" activation (sad to think this is the final season of the beloved show). It was sold out beyond sold out, but generated great awareness as well as blood donations for a good cause.
Or with Amazon Prime's Good Omens, which took over a huge corner across from the Austin Convention Center to set up their "Garden of Earthly Delights" (including a Hellhound Puppy section- so cute!) There were even roving groups of angels roaming the streets of downtown.
But my personal favorite was the Vampire Library for FX's WHAT WE DO IN THE SHADOWS. There were 2-3 of these small freestanding kiosks set up at various locations across Austin from March 9 - March 12.