Shots is a magazine published in Minneapolis in the United States that runs a regular competition for readers. There does not seem to be a prize other than a free copy of the publication if an entry is accepted. At least you get to see your work in print in what appears to be a quality publication.
I haven’t seen a copy of the print version, but the images on-line are first class so the full version seems promising.
The publishers do, however, have a sneaky way of boosting subscriptions. If you want to enter the competition there is a $US15 submission fee (for up to 12 images) if you do not subscribe. Entry is free if you do.
The theme for the next issue is Smoke & Mirrors. You can get full details at http://www.shotsmag.com