The valknut, valknutr, valknot, or "knot of the slain," is an ancient Scandinavian symbol devoted to Odin.

For this drawing, in addition to shading each triangle to distinguish them from each other, I drew various phrases in runes. They're transliterated English, so they're hardly authentic, but they still look decent.

They are:

"In Odin's name,
In Odin's time.

"I hear the call,
I enter the hall.

"My choice is here,
my path is clear."

"Urdh, Skuld, Verthandi."

That last phrase is simply the names of the Norns, who govern Wyrd and Orlog.

BTW, just so's you know, people who wear this symbol generally do so to let Odin know that he can take them at any time.

If you truly don't have a problem with that, here's the image available on a t-shirt: [link]