Officially, my boss calls me a Unix Systems Engineer. At the place I'm outsourced to, I don't really have a title, except for Interchangeable Technical Underling.
Personally, I think of myself as a Unix System Administrator, with the scars to prove it. To a non technical audience, I usually describe myself as an 'IT person'. Amazingly, that seems to keep most of the 'Oh, great, can you fix my printer|scanner|computer|microwave|electric toothbrush)' at a comfortable distance (though that can also be thanks to my ugly mug :) ).