A "Splinter Cell" (in this context) is when you do something particularly sneaky/a physical activity that is a little unusual and difficult. I don't mean anything kinky, just like climbing a pipe that other people have only dared each other to climb, stealthily getting past someone to get something/do something. Like that.
These are also known as a "Hitman" or, more rarely, a "Solid Snake".
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Just to make sure no one has been gullible to the 10th power, I was just joking about the whole saw-blade thing.