Stuff from boxes.
I'm something of a giant robot junkie, and so when I first came across the Exoforce Lego sets I was all over them. And, then I promptly forgot about them. Including, for the longest time, the six kits that I'd actually picked up. Digging through I box that I'd packed back in 2007, I came across them again. None have been assembled yet, although I did open the Stealth Hunter (which is why the box isn't standing up) to look at the instructions.
What made the Exoforce kits cool, outside of their sheer giant-robot-ness was the fact that they had alternate builds - either they combined with another kit or could be assembled into a different form. Sadly, the instructions for the alternates were web-based, and the site is no longer active (although Lego still owns the URL). Another interesting bit about them is that they have actual knees that bend - a feature that no longer appears to be built into current Lego Mecha, judging from mechs in the Ninjago, Teenage Mutant Ninja Turtles and DC Superheroes lines.
Right now, I'm trying to make up my mind as to whether or not I want to actually assemble these guys. The main thing that's stopping me is that I wouldn't have any place to put them, other than my kitchen table, when done with them - so I'm holding off. (Besides, I need someplace to put Orthanc when I assemble that monster.) My co-workers who are into Lego are also pressing me not to build them. "If you don't open them," they point out, "they're worth more money." And while I get the investment aspect, I think I prefer them as toys.