It's mentioned often throughout the series that the name Michael Westen is notorious throughout Russia. Russian Intelligence talks about Michael Westen as having done too much damage to be one person (they think "Michael Westen" is a code name for a Special Operations team) and they use his name and tales of what he's done to scare rookie operatives.
During his 15-year tenure as a spy Michael worked mainly in eastern Europe and the Middle East. As a result he speaks fluent Russian and Farsi and describes his command of the Polish language as rusty. He doesn't know Spanish and is mocked repeatedly throughout the series for living in Miami without being able to converse in Spanish.
In the first season Michael says he's had 30 years of karate training but throughout the series Michael also uses a variety of mixed martial arts including (but not limited to) aikido, Brazilian jujutsu, and the Russian martial art sambo. Michael says he has "combat experience on 5 continents" and "two black belts."
The gadgets "built" by Michael are fabricated by the Special Effects Department. It is a collaborative effort by the writer, production designer, special effects and the prop master. The actual builder is Michael Doyle, the Special Effects Foreman.
The trivia items below may give away important plot points.
In the final episode of burn notice, Fiona and Michael are in a cottage. That same cottage was In the movie The Holiday 2006. It was the setting of Kate Winslet's home in England. Even the road scene leading to the cottage is the same.
Sharon Gless (Madeline) and Tyne Daly were known for their roles in Cagney & Lacey. Daly makes a cameo appearance on Burn Notice as Tina, an asset Madeline cons into giving her information. She then becomes good friends with Tina before having to burn her under Michael's order.