Frost resistance

Frost resistance is useful in Naxxramas and PvP and vs. some undead mobs that have frost powers. In BC, many of the naga casters use frost spells. The first boss in Serpentshrine Cavern required one tank with heavy frost resistance and two with at least some.

• Hunter: Freezing Trap, Frost Trap
• Mage: Blizzard, Cone of Cold, Frost Nova, Frostbolt, Ice Lance, Waterbolt, and Water Elemental's Freeze
• Shaman: Frost Shock

The in patch 1.11 implemented Argent Dawn Frost Resistance items are a bit hard to obtain but are quite useful in frost based encounters (e.g. Naxxramas)

• Cloth: Glacial item collection.
• Leather: Polar Leather item collection.
• Mail: Icy Scale Mail item collection.
• Plate: Icebane Plate item collection.