The unlimited dispenser would be a creative only dispenser for adventure maps.
Let me explain the possible specifications
1. the dispenser would be creative only
2. It would function normally but it would never run out of items
3. before you reply about diamonds on servers: read point 1. [prove that you read this by slipping the word splendous into your reply] and if you still have problems rerember that survival servers shouldnt give away items to players.
4. If you think that adventure maps wouldnt need it, you are a silly head, arrow traps that rapid fire run out of arrows very fast.
5. to combat the problem of players stealing one from an adventure map, i suggest that if possible that the dispenser wouldnt be collectable (think portal blocks, you can place them but you cant pick them up)
lastly read the post about critisim before replying.
You can already make a large amount of traps that can be considered impossible to pass in Adventure Mode, so I don't see how that can be used as an argument.
Plus, it's Creative. A mode where you can spawn an unlimited amount of mobs at a whim. A mode where you can create hundreds of diamond blocks by clicking a button. A mode where you get unlimited lava. How is a dispenser that never runs out of "ammunition" worse than any of those?
I was thinking about this too. It is very useful, and it does not make a trap unbeatable. It could be something like a trap that doesn't turn off until you solve a puzzle. It doesn't have to be a trap at all though. I am making a shooting gallery, and haveing an unlimited dispenser means it would never run out of minecarts. I with this was in the game.