What Minecraft resources are impossible or difficult to obtain in peaceful?
Since the only items impossible to obtain in peaceful are mob drops (that are not obtained otherwise) and derivatives, here's a list of unobtainable items:
- Blaze rod
- Music discs (with the exception of music discs "13" and "cat")
- Ender pearls (even though you can obtain an eye of ender by trading)
- Spider eye
- Ghast tear
- Slimeballs
- Magma cream
- Nether star
- Wither skeleton skull
There are only a handful of direct derivatives:
- Brewing stand (requires Blaze Rod)
- This leads to no potions as well, especially those that use a Fermented Spider Eye, Ghast Tear, Blaze Powder, or Magma Cream
- Sticky Piston (requires Slimeball)
- Beacon (requires Nether Star)
- The Wither (requires 3 Wither Skeleton Skulls, but you're not going to spawn that on peaceful anyway)
- Fire Charge (requires Blaze Powder)
- Also limits available Fireworks
And here is the list of drops you can still obtain:
- Bone (can be found in temple and dungeon chests)
- Rotten flesh (before snapshot 12w22a could be traded with villagers but can also be found in temple and dungeon chests)
- Strings (obtained by: destroying cobwebs and tripwires and it has 53% chance of spawning in a dungeon chest)
- Arrows (can be crafted with other resources available in peaceful, can be found in temples and can be traded with villagers)
- Gunpowder (will be possible to loot in dungeon chests)
- Gold nuggets (can be obtained by placing a gold ingot into a crafting area)
- Dragon egg (reaching the end is possible by trading eyes of ender with villagers; apparently the ender dragon won't despawn on peaceful and the creation of a piston is still possible)
- Glowstone dust (can be obviously obtained in the nether and by trading with villagers)
It is also to note that a lot of items, that are possible to obtain, won't be renewable anymore, like:
- Bone (previously farmed by killing skeletons or wither skeletons)
- Coal (not charcoal, previously farmed by killing the wither skeleton)
- Gunpowder (previously farmed by killing creepers, ghasts or witches)
- Strings (previously farmed by killing spiders and cave spiders)