The "Kaiyodo" name is the creator of detailed sculpts in dynamic poses. They have produced mainly 4 types of pokémon figures:
Trading Figure Game: The TFG had a very short run, as the game turned out to not be very popular, and the figures themselves are delicate and break easily. The first set, Next Quest, was released in 2006/2007... and the game was soon cancelled. The second set, Groundbreakers, was already in production but never had a chance to be released. However, the Groundbreakers figures somehow found their way onto the internet on sale. Many collectors now own these unreleased figures! Additionally, a third set was also announced before the game's cancellation. Figures from this set can also be found (they are believed to be un-official copies of the prototypes). Naturally, all of these un-released figures are very expensive, with some of them selling for nearly $100.
Chess Pieces: This is a set of 25 figures released in 2005. Each one came with colored checkers-like pieces and instructions for playing the game (I'm not sure if it's like real chess or a new game -- I can't read Japanese). Lots of people try to make their own pokemon chess pieces, but here is the real thing. :P By the way, be wary of buying these on eBay (as with everything) - they glue other figures on the bases and make terrible bootlegs.
Bottlecap Figures: These were originally released with the theatrical releases of the movies in Japan. There was also a special 10th Anniversary set that included Pokémon from the first 10 movies. As of Gen 5, they started selling bottlecap figures in the US together with TCG card packages!
Pre-Order Figures: These figures were given out as bonuses for pre-ordering the main games. It started with Diamond & Pearl in Japan, and with Platinum version in the USA (possibly other countries too but I am not sure which).
I like collecting these figures for their level of detail and their cool, dynamic poses!
Except for the TFG, they are also not very difficult to find. A full collection is very costly, though.