Going from left to right, probably number 3, the left one in the second row.

Vertical stripes have too much going on so 1 and 6 are out. 2 is nice and I like how the hammer and sickle is on the left side but the colors don't vibe too well with me. 3 is nice and I like it more than 5 because the triangles are slimmer and more subtle. 4 is good too but it might be better if the star was above the hammer and sickle.