If you've been building kits for a while, you've probably run into Monogram at some point. Their kits tend to show up pretty often when you're looking for classic subjects for sale, especially aircraft, cars, and military pieces that have been around the hobby for years.
A lot of builders stick with them because the kits go together well and still hold up, even compared to newer releases. You can find more in model kits or browse die-cast models when adding to a collection.