(idea credit to FamousZAmos but he was too slow to post a suggestion)
Pretty simple and fun suggestion, basically items/weapons with custom names should display global/world kill messages. Kill messages are generally presented as follows with named items:
(Player 1) was slain by (Player 2) using (Named Item)
FamousZAmos was slain by KlutchDecals using Ban Hammer
To avoid people using vulgar names, have the normal chat filter apply to the death messages. If people named their sword in a way that circumvents the filter, punishment would apply as it does for circumventing the filter normally. Due to the low (but still notable) amount of kills that are made in Meepcraft, the added risk of people attempting to circumvent the filter this way would not be a large problem at all.
If this is easy enough to implement, it would be a nice fun feature that would add a little spice to PvP