David Martin's world: Tasers, ray guns & nerve gas

In the line of duty, correspondent David Martin has been zapped by ray guns and exposed to nerve gas, but when it came to his story this week on 60 Minutes about Tasers, David took a pass -- choosing not to be zapped by painful jolts of electricity.

Watch David Martin's report by clicking here.

This week on Overtime, we take a look at some of David's other adventures. For example, in 2006, David learned how to eat a grub -- a beetle larva -while on training with Special Forces. "It's not bad," David said about the grub he picked from under a rotten tree stump.

Other assignments were more dangerous. In order to find out how American soldiers were being trained to protect themselves from an enemy's use of chemical weapons, in 2002 David suited up in protective gear and joined the soldiers as they were exposed to a nerve agent.

And in our final Overtime excerpt, this one from 2008, David used plywood and even a mattress as he tried to shield himself from a non-lethal weapon called a ray gun - which shoots out a 100,000 watt beam. After getting zapped a few times, David said: "It felt like scalding water."

The person chiefly responsible for putting David into these painful and sometimes dangerous situations is his longtime producer, Mary Walsh. They've been a team for nearly 20 years, reporting from all of the world for the CBS Evening News, 60 Minutes, and other CBS News broadcasts.

One of Mary and David's stories took them underground to one of the many tunnels dug by the North Koreans under the DMZ zone with South Korea. Over the years, the South Koreans have discovered several of these tunnels, dug by the North Koreans presumably to be used in a surprise attack against the south. Here are David and Mary at one of those tunnels.

"We first worked together in 1992 when Sen. John Kerry went to Vietnam to talk to the government about missing Americans," Mary told Overtime. "It was a big breakthrough trip for the U.S. I was a producer in Tokyo at the time. After that I went to Bosnia and Somalia, talking with David on the phone about U.S. military operations -- and eventually convinced him he needed me to be his producer."

Mary began working fulltime as David's producer in 1993, and they've been reporting extraordinary stories ever since. Says Mary: "We were with the first U.S. combat troops in to Bosnia in 1995; covered the wars in Iraq and Afghanistan; and covered U.S. military operations in Japan, Korea, Turkey, Haiti, Germany, Italy -- and probably more."

Together, Martin and Walsh have won two DuPont Awards and one Emmy Award for their work.