I don't know if this is a word, but I'd say I am a "possibilist." I immensely enjoy doing things that are impossible. And aside from silly logic games like the immovable object versus the unstoppable force, I tend to believe that most things are possible, that most problems are solvable, even if we can't do it now.
However, regrettably, I would say that it is impossible that the Witnesses are right. This does not reflect bias on my part. It reflects an impossibility for me to "unknow" all the things that show that they are totally, totally wrong. And even if I did suffer some sort of amnesia, it would only mean that I forgot that they were wrong, not that they were actually right.
It is nearly impossible for me to speak to fundamentalists and not roll my eyes more than I should. I can muster it, but it is a challenge.
It has proven impossible for me to have the same level of interest in video games as I did when I was 14 years old. This could change, however, with the advent of holodeck-style technologies.
I believe it will be impossible for me ever to convert to any form of religion.
To answer your question seriously, actually, when I think about it, I'm not willing to say many things are impossible. Even the items on your list, which I have a very high degree of confidence in, might be possible. In practical terms, I am utterly convinced that the dead cannot kill the living. But my experiences with absolutism instruct me to always hold out the possibility, however absurd the position appears to be, that things might be different than they appear. That is to say, almost all of my beliefs are provisional, based of the evidence at hand.
I say, "almost all my beliefs" because there is one class of belief that does not require provisional conviction. I think you gave the best example of that recently in your comment about bats. It is commonly believed that they cannot see, when in fact, they can see just fine. After having learned the fact, how could one possibily revert to the old position? (Actually, I must admit that I know nothing about bat sight, so this example is based on the supposition that your example was accurate. But it illustrates the point: it is not possible to revert from knowledge to ignorance.)
And that is why the one absolute conviction I have is that the Witnesses are not what they claim. I have a very high degree of conviction that other religions (such as Mormons) are also not what they claim, but because my experience and research have been most highly focused on the Witnesses, they are the only ones about which I can honestly and uninhibitedly say I have sufficiently complete knowledge to make this (rare) absolute statement.