Cybercon III

Amongst the first batch of FPS it was released in 1991 - It was a shooter with puzzles and had shades of  System Shock about it. You could pick up and drop objectives, store them in your back pack  and use them later and also change camera view. Lots of good ideas to be eventually used by other developers. Clever stuff for it's time.

Walkthru here:

http://www.gamewinners.com/walkthrough/cybercon3/index.html