BonnieJP

I have used sport team colors. You can purchase licensed team fabrics (Chicago Blackhawk quilt) or just go with the team colors like the orange, navy and white (Chicago Bears). The advantages of going with team colors rather than the licensed fabrics are the plain fabrics are easier to find, usually cost less, and may or may not represent a sport team, depending on the recipient's view point.

CanoePam

Good for you at making things for boys/young men. There are more boys in foster care and NICUs than girls, but too few quilters think of them. I concentrate on male quilts too (something about having three sons …). I use batiks in browns, greens, golds, blues, grays, etc, just not pink or flowers. I use a lot of “read as solid” prints - grunge is a particular favorite. Paired with a novelty print of some type it works well. Any any pattern other than things like Sunbonnet Sue or Flower Basket will work in the right colors.

lindaschipper

How about going to thrift stores and collecting men's shirts to cut up and make a patchwork quilts from. Even a simple pattern turns out beautiful. There is a lot of fabric in these shirts that have been washed and softened already for you. Bloggist Jo Kramer makes beautiful quilts from shirts like these.
And just a note...not every teenage boy skateboards!

wesing

You can never go wrong with stars and Americana.

Wood Sprite

So many masculine designs come to mind. It's all in the fabric that's selected. Some ideas:

A mix of different plaid fabrics cut into simple squares. (I LOVE this look and definitely prefer masculine to feminine designs.)

Hunter's Star, Carpenter's Star or similar pattern.

Brick or block pattern in any medium to dark colors/prints.

Pixel designs of whatever is currently hot with that age group. (Computer game characters?)

A simple jelly roll race.

Stack & flip.

Half square triangles arranged as pinwheels, chevron or other layouts.

Strip tubes give a lot of design options.

A simple background with one medium- to large-size applique of something sports related (baseketball, football, baseball and bat, hockey sticks, etc.).

A simple background with a few appliques of something outdoorsy/woodsy (howling wolf, fox (non-cutesy version), owl in a tree, fish swimming or jumping, deer (head with nice antlers or side view of whole deer), etc.).

Rail fence.

Just simple horizontal strips of various colors or prints. I really like the "Quick Strippie" from Mary's Quilts blog.

Even something like 9 or 16 patch in bright, happy colors sashed in black would be nice for a young man that likes colorful things.

Scrappy quilt of simple squares or rectangles.