using /summon ~ ~ ~
with some block ids like water, doors, saplings to not render or render weird.
Blocks with flat textures held by player in third person view, villager / iron golem or enderman have z-fighting
Some blocks are invisible in enderman's hands
Thin black stripes over mooshrooms / iron golems / enderman / falling block with mipmapping
Stained glass held by an enderman is opaque
End Portal Block not rendered when enderman hold it!
End portals and end gateways held by endermen or as block display entities are not rendered, but nether portals are