Lethal Tender

Secret agent Nick Hunter must thwart the evil Thorne Devereaux, who is planting bombs in U.S. currency. The game featured various singular features such as taking the uniforms of dead enemies for protection. The game is described by Home of the Underdogs as a "a fun, albeit amateurish, first-person shooter." The game set out the style followed closely by most other Pie in the Sky engine games, particularly noting its inventory system, though even its graphics were mostly reused by later games as well. The game is also known as Legal Tender.

Source: Wikipedia, "Pie in the Sky (game engine)", available under the CC-BY-SA License.