With their promising electronic, mechanical, optical and thermal properties, carbon nanotubes have been the subject of intensive research for over twenty years now. Yet, there remains much to learn about and from them. In this talk, I will describe some of our unusual findings on the interaction of light with nanotubes. In particular, I will discuss how light-induced heat could become trapped in conductive carbon nanotube arrays, in sharp contrast with what we are used to in bulk conductors, and describe a thermionic solar cell and some other applications based on the effect. I will also show how these arrays, known to be the darkest man-made materials, can easily be turned into mirrors. Time permitting, I will then slightly change the topic to the interaction of energetic electrons with carbon nanotubes, discuss differences and similarities compared to such interactions with bulk solids, and describe some of the surprising effects in this context and their possible applications.