I'll pass on the chlorine trifluoride

One of the more interesting aspects of safety industry is the tales of danger that you pick up from fellow professionals and experience. I once heard of a response team finding a leaking can of potassium cyanide nearby a growing acid spill. They ran out and got the full self-contained breathing apparatus before going any further.

There are some experiments and chemicals which make that look like a picnic. These include condensing hydrogen cyanide and compounds that explode without much of a reason. And chlorine trifluoride

I have not encountered this fine substance myself, but reading up on its properties immediately gives it a spot on my “no way, no how” list. Let's put it this way: during World War II, the Germans were very interested in using it in self-igniting flamethrowers, but found it too nasty to work with. It is apparently about the most vigorous fluorinating agent known, and is much more difficult to handle than fluorine gas. That’s one of those statements you don’t get to hear very often, and it should be enough to make any sensible chemist turn around smartly and head down the hall in the other direction.

The compound also a stronger oxidizing agent than oxygen itself, which also puts it into rare territory. That means that it can potentially go on to “burn” things that you would normally consider already burnt to hell and gone, and a practical consequence of that is that it’ll start roaring reactions with things like bricks and asbestos tile. It’s been used in the semiconductor industry to clean oxides off of surfaces, at which activity it no doubt excels.

Whoa... (Emphasis mine, taken from here)

You can see more like these here. It is a great little list of nasty substances.