1.9.2 Customized Mobs | Command Block

Video:

Commands:
1. /summon Slime ~ ~1 ~ {Size:3,Passengers:[{id:Zombie,CanBreakDoors:1,HandItems:[{id:"minecraft:diamond_sword"},{id:"minecraft:diamond_sword"}],ArmorItems:[{id:"minecraft:diamond_boots"},{id:"minecraft:diamond_leggings"},{id:"minecraft:diamond_chestplate"},{id:"minecraft:tnt"}]}]}

2. /summon Slime ~ ~1 ~ {Size:1,Passengers:[{id:EnderCrystal}]}

3. /summon Guardian ~ ~1 ~ {Elder:1,Passengers:[{id:Witch}]}