Cube World.
I personally find those kinda boring. They don't do much after you get past the mildly amusing 'tilt-and-fall' thing it does. Mind you, I could go for ages watching that little stickman fall from side to side in his box.
I actually couldn't name a favourite singular toy. I guess all I've ever done with toys, is assembled them together, and played with all of them. I tend to make out storys and motives/alliances between the toy types too. Like, Matchbox/Hot Wheels cars do not like Legos. Legos don't like Army Men. No one likes Star Wars guys (Cause they're so dangerous) and then the odd bits and bobs just work around with the rest.
It would probaly be a mix with my (once) large set of lego mini-figs and some 'Ice Explorers?' that I'd play with the most. Mainly because the Mini-Figs were small and I could give them custom-made vehicles, and because the Ice things had a Giant truck (We had two) which was perfect sizing for 16x16 Baseplates. We also had Three Mammoths from the same set. On one of them, if you pushed its head down, it made 'Elephant-Roaring' noises. Now that's cool.
I unfortuantely lost a large amount (80%) of my good Mini-figs due to a freak 'boating' accident.
Ok, I lost them in the summer, outside when we had a pool up. :/