Those items are parts of the Monster's Loot Mutator installed in the Monster Mash servers. They give you various items, weapon, ammunition and unique artifacts useful in RPG Invasion.

1. Unique Artifacts

Cry of Repulsion 

Enhance Weapon Enchantment Charm

Fiendish Relic

Infinite Weapon Crafter

Reloading Weapon Crafter

Resupply Prism

Memorial Star

2. Experience Shards

Blue Experience Shard

Green Experience Shard

Red Experience Shard

Golden Experience Shard

3. Weapons Drop

ZenCoders MP5

Spider Mine Layer

Link Gun

Redeemer

Ion Painter

4. Adrenaline 

5 Adren Multi Adrenaline (Green)

10 Adren Mega Adrenaline (Yellow)

20 Adren Ultra Adrenaline (Blue)

5. Healths 

10 HP Health Vials (Green)

20 HP Health Vials (Orange)

50 HP Health Pack (Green)

200 HP KegO'Health (Green)

6. Shields

50 AP Shield Pack (Yellow)

100 AP Super Shield Pack (Yellow)

7. Double Damage

15 sec. Double Damage (Orange)

30 sec. Double Damage (Purple)

8. Misc. Items

Ammunition Crate

Mana Spirit

Omni Ammo Canister