I love this song by the Afro-Cuban All Stars, and not just because it has a great beat. (lyrics)
Yo le puse el corazón // también le puse la mente //
y el producto resulto // bien distinto y diferente.
I put my heart into it // and also my mind;
the product that results // is very unique and different.
A lot of the value I bring to a test team (or indeed any team) comes by virtue of being different -- of bringing a different life experience, different perspective, and different set of skills to the table.
To take another angle, I've worked as a programmer, sysadmin, and a tester in recent memory. While I'd likely lose out on a kernel hacker job to someone who's spent the last 20 years coding in C, small shops (like the one I'm in now) really appreciate having someone around who can kick servers together, debug CMS modules, and come up with testing tools for the open source project we're hacking on. So it goes with other aspects of my background -- knowing i18n and a few snippets of Japanese because of my time as an exchange student; being sensitive to the ethical ramifications of a piece of software on account of my background in Philosophy; thinking things out in terms of concepts, theories, principles, and strategies, because that's simply how my mind works.
It may be presumptuous to think that you can be the best programmer in the entire world, or the best tester, or what have you. But you can be the best you in the world; the best at at offering the unique set of skills and perspectives that only you have. Though I endeavour to give my best, I'm not so presumptuous to think that I am the best. But I hope you will always find my work distinto; diferente.