I had 2 favs.
On the OLD Atari console: Adventure. Before I took the chalice into the castle, I'd always go around collecting things in the castle. The bridge, the keys, the weapon, the dead dragons (YES, the dead dragons! Grab the bat and keep taking it back and forth across the corpse until it picked up and make sure you had something in your vault the bat would grab. At some point, the bat will let go of the corpse). If I remember, you can even lock the poor bat IN the room.
On the Commodore 64/128, Temple of Apshai Trilogy. I liked the one region where you had to face the basilisk (or get around it without dying) and you picked up the most profitable treasure. It was 10,250 in price. When you got back and sold it, the music was much different than you had before (I do wish there was a way to hack the sound from it). Of course, if you died, your character fell to pieces in a pile.