I made a spider web design in browns for one son and a snails trail in black and orange (school colors) for the other. They both liked them and they were teenagers at the time.

I just finished a quilt for a boy - it's from the Missouri Star Quilt Co tutorial - Sail Away. Here is a link. Hope you can find it. It is sure cute and quite easy to make. I didn't get a picture of it before I gave it away, but hoping to get one soon.
http://www.youtube.com/watch?v=o76gA...69C28&index=40

Boys that age don't know much about airplanes with propellers. Tell them they are helicopter blades. They'll understand that.

Pinwheel can look masculine if you choose "guy" colors, i.e. no pastels. If you chose all greens, browns and gray, it would look like camouflage.

I agree with this. I think my boys like triangles and pinwheels would not be girly at all with the right colors.Still I think you should do something else maybe because you seem to feel they are girly or maybe not right. Oick something you feel is the right pattern. there are so many options.

the pinwheel can be boy-ish. warmer colors and neutrals. I am making a warm wishes patter with dogs today. made a girly warm wishes last month. different look only because of the fabrics. I agree with the comments that encourage you to just pick out fabrics of the boys liking and it will be enjoyed.

I used a dresden plate pattern for a boy, I told him it was helicopter blades, he loved it!

Jenny Doan has 2 "disappearing pinwheel" quilts. They are essentially the same pattern but the pieces of the blocks are placed in different positions. Both patterns are easy and should work well. The resulting blocks are large and would work up quickly. Hope this info helps.

Warm Wishes come to mind, plus sometimes a simple 9-patch with a plain square of fabric with a theme or hobby that they enjoy.

I'm making this with flannels. It is very male looking. I think using plaids helps a lot. This quilt isn't finished. I have to put on piano keys and another border before I send it to the LAQ. It has so much red, but it reads as male, don't you think?