Raptor: Call of the Shadows is one of the best Dos-based vertical shooters ever made. The concept was simple and quintessential to a period of gaming where you configured your sound card and never stopped shooting. It was also fairly advanced for its April 1, 1994 release date. It had stunning graphics, background music and tons of individual sound effects from machine guns to missiles to explosions. The plot was simple — you were a mercenary paid to eliminate “MegaCorp’s” competitors. Take it from 3D Realms: “In the future as a mercenary flying the super-tech Raptor, you’ll be sent on interplanetary missions to knock off top competitors of MegaCorp. Battle against hordes of relentless enemies. Spend the bounty you receive from their demise to expand your devastating arsenal, which can be upgraded with 14 hard core weapons!” Raptor was mostly a keyboard-controller game but it supported mouse movement, joysticks and gamepads.
The shareware episode of Raptor: Call of the Shadows, for DOS. In this game you shoot up the planes that are worse than yours and take their money and upgrade your own, and then rinse and repeat!