Originally posted by Requimatic:

The arrows in the chests throughout the Swamp biome are not Flinthead Arrows, they're Ironhead Arrows. They look very similar (too similar..), so don't forget to pick them up!

Like in Minecraft, I hoard as much as I can and will pick up as much as I can. However, thanks for the tip. I'm sure some people might have passed those on, thinking they're regular arrows.