Is it possible to have a perfectly black material? After reading this NASA article about the "blackest material", the following stuck out to me.

The tiny gaps between the tubes absorb 99.5 percent of the light that hits them

Is it possible to create a material that absorbs, not just all visible light, but all electromagnetic radiation?
 A: We can make it absorb a lot of energy but if you read about black-body radiation effect you will notice that as energy is introduced into the object it will similarly radiate a small amount of the energy back, at room temperature appears black, as most of the energy it radiates is infra-red and cannot be perceived by the human eye. At higher temperatures, black bodies glow with increasing intensity and colors that range from dull red to blindingly brilliant blue-white as the temperature increases.
This means that later even if we did have an $100$ percent absorbing materials of all electro-magnetic radiation the object will radiate some energy due to heating or other similar process. That in mind, it will always leak out some energy.To conclude, we could say it will only absorb radiation for short-time before releasing enough photons which could be detected by an photon detector, therefore "breaking" the truly blackest or absorbing material due to this effect. 
As a summary as long as the object absorbs some form of energy it can never be completely black. 
To learn more pertaining black-body radiation, read this: http://en.wikipedia.org/wiki/Black-body_radiation
Furthermore, an blackhole is very black however it even is not as the power in the Hawking radiation (if it was proven, currently it is hypothesized) from a solar mass $M$ which is equal to $1.98855\pm 0.00025 * 10^{30}$ black hole turns out to be a minuscule 9 × 10−29 watts. It is indeed an extremely good approximation to call such an object 'black'. As 
$$
P =\hbar c^2/15360\pi G^2M^2 = 9.004 * 10^{-29}
$$
That being said, even black-holes one of the strongest objects cannot escape being truly  black. 
A: I believe user43495's answer to be quite accurate, and right, but I will add something here just as food for thought.
It has been hypothesised that the LHC could create miniature black holes. Even if it can't, there are many in space[citation needed]. These would be able to "absorb" all kinds of electromagnetic radiation. Within a black hole's event horizon, escape velocity is higher than the speed of light. Black holes are black bodies, but even their own radiated photons cannot escape past their event horizon. That should be as dark as you can get.
Stephen Hawkings has some works where he describes a kind of radiation emanated from black holes. Editions in italic: the existence of this Hawkings Radiation has been not been proved true or false yet. But supposing it exists, it is a kind of black body radiation. However, its energy is not proportional to temperature as in most black bodies. Rather, it's inversely proportional to the black hole's mass. I think with sufficient mass, a black hole may be darker than the material quoted in the question.
(Thanks user43495 for reminding me that Hawkings Radiation is still hypothetical.)
