First two to come to mind were Babcock and Bylsma.
“The most terrifying fact about the universe is not that it is hostile, but that it is indifferent. If we can come to terms with this indifference and accept the challenges of life within the boundaries of death, our existence as a species can have genuine meaning and fulfillment. However vast the darkness, we must supply our own light.” - Stanley Kubrick
Babcock is as safe as you can get. No way he leaves unless he wants to.
Pretty much the same goes for Bylsma right now.
Trotz constantly does a lot with not much, so I'd say his job is pretty safe.
Ruff's tenure is amazing, but the Sabres are very solid this season and if for some reason they faulter, his job wouldn't necessarily be at jeopardy, but some questions may be asked.
I added Quenneville simply because I wanted to make it the Top 5. He's a solid coach with a cup win.