I like the Black Hole Burr ("BHB") because its one of the few interlocking burrs that I can actually solve without Burr Tools or other aids. Plus the fact it has only 3 board pieces and a black "block". Not as intimidating as one might imagine.
The BHB was Rosemary Howbrigg's IPP34 Exchange Puzzle. It was designed by Junichi Yananose and produced by Brian Young of the new revamped Mr Puzzle. The three board pieces are made of laser cut acrylic and the block is wood painted black. Quality of construction fit and finish is excellent and everything fits and slides nicely.
At first glance, it doesn't look too difficult, after all, its only three pieces. But believe me, its more difficult than it looks. Its not too hard to get the three acrylic pieces together without the block and that is what I tried to do first, so as to get a feel of the orientation of the pieces and how they interact with each other and how the block might fit into the centre. Once I had figured this out, I then sorted out the fit of the block.
Having solved the BHB, while its not as difficult as I had expected, its no walk in the park either, at least not for me. And take a hint here; Burr Tools won't work for this puzzle (So you probably know what's involved).
Its a tricky puzzle made more challenging by the fact that the pieces are transparent acrylic, making it harder to see the outlines of the pieces and where they join/intersect etc. My less than perfect eyesight, especially at night doesn't help either.
Overall a well made burr puzzle that provides a nice challenge that does not overly frustrate; the type that one would classify as having "just the right amount of difficulty for an exchange puzzle".
Available from Mr Puzzle for AU$30/-.