Run and Gun Shooters are really a mix Shoot Them Ups and Platformer genres and can be argued why include them on a Shoot Them Ups Wiki. However, design of the games and many of the 'ism' of most of the game lend themselves to this wiki.
Run and gun usually describes shoot 'em ups where the player character runs on foot, often incorporating jumping, as seen in platform games. Run and gun games can utilise side-scrolling, top-down or isometric viewpoints. This sub-genre was popularized by Konami's classic Contra. Gunstar Heroes and Metal Slug are also among the most popular examples of this style. Side-scrolling run and gun games are an attempt to marry platform games with shoot 'em ups, characterized by a minimal focus on precise platform jumping and a major emphasis on multi-directional shooting. These games are sometimes called platform-shooters. This genre has strong arcade roots, and as such, these games are generally known for being very difficult, and having very linear progression, without backtracking.
There are games which feature a heavy degree of shooting but do not fall into this sub-genre. Mega Man, Vectorman, Jazz Jackrabbit , Earthworm Jim and Turrican are all platformers with a heavy focus on action and shooting, but unlike Contra or Metal Slug the platform jumping elements, as well as exploration and back-tracking, still figure more prominently. Run and guns are generally very pure and, while they sometimes have vehicular sequences or other changes in style, they stay focused on shooting throughout.