I want to know what people's favorite perk or perks are.
For me it's definitely Zanshin Tactics. I play Doctor almost exclusively, and Zanshin is a godsend on him. Denial of resources becomes so much easier when I'm running Zanshin along with a range add-on. I'm not sure if it's just me, but I have trouble identifying long wall jungle gyms from short wall jungle gyms until it's too late and the survivor I'm chasing is already too close to the window for me to deny it. But with Zanshin I can see ahead and plan accordingly!
Not only that, but I can also see routes a survivor might take at about the same time they do even though I'm far behind them because I can see their resources through walls. It's ESPECIALLY nice on indoor maps, Léry's in particular. There are so many windows in that map I don't know about until it's too late.
In essence the knowledge that Zanshin gives me is invaluable in terms of cutting down chases.