All classes that implement BlockPluginInterface

class \Drupal\aggregator\Plugin\Block\AggregatorCategoryBlock
class \Drupal\aggregator\Plugin\Block\AggregatorFeedBlock
class \Drupal\block\BlockBase implements BlockPluginInterface
class \Drupal\block_test\Plugin\Block\TestBlockInstantiation
class \Drupal\block_test\Plugin\Block\TestCacheBlock
class \Drupal\block_test\Plugin\Block\TestHtmlIdBlock
class \Drupal\block_test\Plugin\Block\TestXSSTitleBlock
class \Drupal\book\Plugin\Block\BookNavigationBlock
class \Drupal\comment\Plugin\Block\RecentCommentsBlock
class \Drupal\custom_block\Plugin\Block\CustomBlockBlock
class \Drupal\forum\Plugin\Block\ActiveTopicsBlock
class \Drupal\forum\Plugin\Block\ForumBlockBase
class \Drupal\forum\Plugin\Block\NewTopicsBlock
class \Drupal\language\Plugin\Block\LanguageBlock
class \Drupal\menu\Plugin\Block\MenuBlock
class \Drupal\node\Plugin\Block\RecentContentBlock
class \Drupal\node\Plugin\Block\SyndicateBlock
class \Drupal\search\Plugin\Block\SearchBlock
class \Drupal\shortcut\Plugin\Block\ShortcutsBlock
class \Drupal\statistics\Plugin\Block\StatisticsPopularBlock
class \Drupal\system\Plugin\Block\SystemHelpBlock
class \Drupal\system\Plugin\Block\SystemMainBlock
class \Drupal\system\Plugin\Block\SystemMenuBlock
class \Drupal\system\Plugin\Block\SystemPoweredByBlock
class \Drupal\user\Plugin\Block\UserLoginBlock
class \Drupal\user\Plugin\Block\UserNewBlock
class \Drupal\user\Plugin\Block\UserOnlineBlock
class \Drupal\views\Plugin\Block\ViewsBlock
class \Drupal\views\Plugin\Block\ViewsExposedFilterBlock