>So, I'm selling a watch on WatchUSeek, I visit your site, pay $20 to get listed in the featured row on the watches category for a week.

>I'm still scratching my head on the gun section though since it's very poplar but I can't run AdSense in that category

Popular gun forums are on the same boat and that's why their side-bars are filled with advertisers/affiliates/sponsors. Just contact those with your numbers on the sub-section, i'm sure you'll sell out quickly.

Your website has a lot of potential for targeted advertising.