Robots
Everyone had a transformer, perhaps better known by their individual names like Soundwave and Optimus Prime. Although these toys were popular in their own genre and not so rare, certain models are difficult to find: Fortress Maximus is an example. This was one of the biggest transformer toys ever made at two feet tall and was also the most complex toy to assemble.
Card Games
Popular anime series typically have a lot of spin-off merchandise like action figures, clothing lines and card games. Card games are the most difficult to find intact and in good shape. In the 1980s, the big giant robot anime series Voltron generated a card game called GoLion. The cards were designed and drawn in an anime style and featured characters from the game.
Video Games
The classic Nintendo video game set is easy to track down at local garage sales or second-hand stores, but the accessories are tricky to find. The Robotic Operating Buddy (R.O.B.) was a part of the original Nintendo system. It was designed to run with particular video games, but hardly any games were released to work with the robot, and they were not very popular.
Retail Availability
Rare Japanese toys can be found readily on stores like eBay and Amazon.com, but do not forget to check your local yard sales and thrift stores for people cleaning out the attic or recycling their old toys. Popular Japanese toys are often based on popular comic books or cartoons and fan sites can also point you towards a certain kind of merchandise. Classic Japanese toys can experience a resurgence of popularity when updated cartoons or movies are released, such as the recent Astroboy or Transformer films.