What is the most massive star?

What is the most massive star that we observe that isn’t a black hole or a stellar remnant?

Thanks,
Rob

Try this page;
http://en.wikipedia.org/wiki/List_of_most_massive_stars

don’t forget to read the caveat on that page - some, many, or most of these stars might be very close doubles.

In particular see this star in the Large Magellanic Cloud
R136a1