The LEGO Jango Fett mini figure is probably the most popular Star Wars LEGO mini figure. Jango Fett himself has proven to be a very popular character from the Attack of the Clones film in the same fashion that Boba Fett was so popular to Star Wars enthusiasts of the original series. Jango is a bounty hunter and considered the greatest in the galaxy.
The Jango Fett LEGO figure comes with two pistols and headgear. The minifigs head is plain black with no features on one side and a face on the other side. The only Star Wars LEGO Set that includes this minifig is Jango Fett's Slave I. This makes Jango Fett really hard to find.
Jango Fett is the "father" of LEGO Boba Fett. Boba Fett is actually a genetic clone of Jango Fett as is the entire clone army, and later the imperial Stormroopers of the Galactic Empire. So basically an entire LEGO Clone Army is actually a bunch of clone of Jango Fett! Both Jango and Boba are considered great bounty hunters and are always playing both sides. In the Attack of the Clones film Jango Fett is killed in front of his son/clone Boba Fett. Boba Fett is obviously devestated by this but uses that as motivation to take over his fathers trade.
The LEGO Jango Fett minifig is a pretty rare LEGO minifig and sometimes sells on auction sites (like eBay) for very much inflated prices. You might find a Jango Fett in auctions that contain lots of LEGO Star Wars figures when searching eBay. Try doing a search in eBay and see if you get lucky! Many eBay sellers do not know the value of LEGO mini figures and so just throw up a bunch for sale at the same time.
Another idea is to just purchase a custom LEGO Jango Fett figure. There are many hobbyists that can take an existing LEGO figure and turn it into whatever figure you want. Many do that with the Boba Fett figure since it is much more common and has the same headgear as the Jango Fett LEGO figure, only painted differently.
