Perhaps the most usable function of them all. Returns or renders a drupal block directly in your template. No need to use context, panels or any other system to have display a block based on certain conditions.

{{ viewblock(delta,module,return) }}

delta the delta of the block you want to render. This could be the only parameter needed if the delta of your block is unique in the block table.

module the module of the block the given delta belongs to. If your delta is a simple number, you need to specify the module the block belongs to.

return Return the block rendered (true) or as a build render array.

{% set menuitems = viewblock(2,'menu_block',false) %}
{# the menuitems variable now contains the renderable array of the menu_block
modules block 2 #}
{# Render the view_block_id #}
{{ viewblock(view_block_id,'views') }}