Mine is Heraclitus, "the weeping philosopher". All we have of his writings are fragments, my favorite being:
He who hears not me but the Logos will say: All is one.
I have hope that with new archaeological discoveries, and with new technology being used to recover old, formerly unreadable documents like burnt paper which can now be read, that there will be more writings of the Pre-Socratics available for us to read in the future.
A mention of Heraclitus is not complete without also mentioning Parmenides[0]. Together, these two are the champions of their respective sides in the millennia old Being vs Becoming [1] debate. Being took a few blows at the hands of modern philosophers but I think there's plenty of room to explore the idea in the contemporary setting. The ideas we have access to now concerning relativity, quantum mechanics, space-time, and the holographic universe make it fun to explore Parmenides's idea of a static, unchanging reality that we are only able to perceive in a limited way due to our fundamental limitations as finite humans.
As a side note, I find it amusing how closely this debate parallels one of our own debates in the programming community: functional vs imperative programming.
To drag this debate down, I find it interesting that in the Marvel universe you could have put "a static, unchanging reality that we are only able to perceive in a limited way due to our fundamental limitations as finite humans" into the mouth of Doctor Doom word for word and it would fit right in ("Books of Doom" has him saying pretty much exactly that to his physics teacher as a teen), perhaps with a few minor changes ("our" to "your", probably, as the character would not want to include himself amongst mere "finite humans").
When the right writers get hold of one of the more interesting characters, there's a surprising amount of nods to philosophy to be found.
http://myweb.fsu.edu/jjm09f/RhetoricSpring2012/Gorgias%20Enc...
We don't have much from the pre-Socratics. We have Plato. History is selective that way.