Place mobs!

Sheep
  Shear sheep --> Place wool
  Dye sheep --> Shear sheep --> Place wool

Skeleton/Stray/Skeleton Horse/Wither Skeleton
  Kill skeleton --> Craft bone into bonemeal --> Craft 9 bone meal into bone block --> place bone block

Mooshroom
  Shear mooshroom --> Kill skeleton (to get bonemeal) --> Use bonemeal on mushroom (on ground)

Spider
  Kill spider --> Craft 4 string into wool --> Place wool

Zombie Pigman
  Kill zombie pigman --> Craft 9 gold nuggets into gold ingot --> Craft 9 gold ingots into gold block --> Place gold block

Witch
  Kill witch
    --> Craft 4 glowstone dust into glowstone
    --> Craft 9 redstone into redstone block
    --> Craft 7 sticks into ladders

Guardian
  Kill guardian --> Craft 4 prismarine shards into prismarine --> Place prismarine
                --> Craft 9 prismarine shards into prismarine bricks --> Place prismarine bricks
                --> Craft 4 prismarine shards and 5 prismarine crystals into sea lantern --> Place sea lantern

Elder Guardian
  Kill elder guardian --> Place wet sponge
                            --> Dry wet sponge in furnace --> Place sponge

Shulker
  Kill shulker --> Craft 2 shulker shells + a chest into a shulker box --> Place shulker box

Vindicator/Vex
  Kill Vindicator/Vex --> Craft 9 emeralds into emerald block --> Place emerald block

Slime
  Kill slime --> Craft 9 slimeballs into slime block --> Place slime block

Zombie/Husk
  Kill zombie --> Craft 9 iron (RARE DROP) into iron block --> Place iron block

Snow Golem/Snowman
  Kill snowman --> Craft 4 snowballs into snow block --> Place snow block

Iron Golem/Villager Golem
  Kill iron golem --> Craft 9 iron ingots into iron block --> Place iron block