Some items are hard to get on direwolf server, and I would love to be able to get it in /market but maybe a chance as votingreward/voteparty would be nice too 
- spawnershards - or broken spawners - maybe even working spawners.. becaue it takes very long time to find enough for your need and with many people online it will be even more and more rare to find a blazespawner in nether.
- runes I like them and they are only cosmetic so wouldnt affect gameplay much - and having to fly through nether for hours for finding chests might cause lag - random colours
- maybe netherquartz - if it becomes too hard to find the ore?