Last year, I was up at the Abu Dhabi Pro Trials. Some of the coaches milling about were guys like Renzo Graice, Lloyd Irvin, Marcelo Garcia, Cyborg (also competed).
At any rate, Marcelo's guys were quick to attack the neck as it's a favorite of their instructor.
If you've read previous posts on here, I like the submissions and takedowns for which I routinely find entries and opportunities to attack in a multitude of places: the arm and the neck seem to present themselves quite a bit. As such I like chokes and armbars.
I also like things that don't come naturally to me. The Guillotine fits all of the above criteria. I've found and gotten together the candidate for Guillotine Master in Marcelo Garcia and below is a HL of his, then him teaching the guillotine from a variety of positions. Now, go attack that neck.
See highlight for examples:
See Marcelo's Guillotine from Sidemount:
See Marcelo's Guillotine from Butterfly Guard:
Aaaaaand, see Marcelo's Guillotine from Mount :) :