Thunderhawk
The standard air support and transportation vehicle for the Space Marines. The transport variant has a big, open area for carrying two Rhinos or one Land Raider underneath it; the gunship variant can hold thirty Space Marines inside, and sports the massive Thunderhawk Cannon on its back. Both variants have missile pylons and remotely-operated heavy bolter turrets.
The Thunderhawk replaces the Stormbird transporter, which is more heavily armed and capable of carrying more cargo than a Thunderhawk Gunship and Transporter combined, up to 50 Space Marines. As the demand for dropships increased during the Great Crusade, the Thunderhawk was created as an easy-to-produce alternative for the Unification War era Stormbirds, though considered inferior in quality. After the Horus Heresy, it was decided that putting one twentieth of a Space Marine Chapter in a single vessel was a bad idea, so the Stormbird was mothballed after the Codex Astartes reform.
The Thunderhawk started out life in Epic as essentially a flying Rhino (in other words, they were METAL BOXES); it had a stumpy battle cannon and wings three scale feet thick. This persisted through a number of horrendous-looking scratchbuilds before eventually someone at Games Workshop had the bright idea of producing a limited-edition £400 Thunderhawk in lead for 40K, with a much longer hull, proper, manly wings, and loads of weapons. These were given away as the non-useless prize for winning Golden Demon along with the usual Slayer Sword a couple of times, until GW saw there was a Market and Forge World took up the slack. Forge World still sells Thunderhawk models, both in Transport and Gunship varieties, with several options for molded livery and (for the Transporter) vehicles to be carried.