Classes descending from StandardError in an unaltered Rails 3.2.13 application.

gistfile1.txt

StandardError
  SQLite3::Exception
    SQLite3::MemoryException
    SQLite3::LockedException
    SQLite3::BusyException
    SQLite3::AbortException
    SQLite3::PermissionException
    SQLite3::InternalException
    SQLite3::SQLException
    SQLite3::NotADatabaseException
    SQLite3::RangeException
    SQLite3::FormatException
    SQLite3::AuthorizationException
    SQLite3::UnsupportedException
    SQLite3::MisuseException
    SQLite3::MismatchException
    SQLite3::ConstraintException
    SQLite3::TooBigException
    SQLite3::SchemaChangedException
    SQLite3::EmptyException
    SQLite3::ProtocolException
    SQLite3::CantOpenException
    SQLite3::FullException
    SQLite3::NotFoundException
    SQLite3::CorruptException
    SQLite3::IOException
    SQLite3::InterruptException
    SQLite3::ReadOnlyException
  FiberError
  ThreadError
  IndexError
    StopIteration
    KeyError
  Math::DomainError
  LocalJumpError
  IOError
    EOFError
  EncodingError
    Encoding::ConverterNotFoundError
    Encoding::InvalidByteSequenceError
    Encoding::UndefinedConversionError
    Encoding::CompatibilityError
  RegexpError
  SystemCallError
    Errno::ERPCMISMATCH
    Errno::EPROGUNAVAIL
    Errno::EPROGMISMATCH
    Errno::EPROCUNAVAIL
    Errno::EPROCLIM
    Errno::ENOTSUP
    Errno::ENOATTR
    Errno::ENEEDAUTH
    Errno::EFTYPE
    Errno::EBADRPC
    Errno::EAUTH
    Errno::EOWNERDEAD
    Errno::ENOTRECOVERABLE
    Errno::ECANCELED
    Errno::EDQUOT
    Errno::ESTALE
    Errno::EINPROGRESS
    Errno::EALREADY
    Errno::EHOSTUNREACH
    Errno::EHOSTDOWN
    Errno::ECONNREFUSED
    Errno::ETIMEDOUT
    Errno::ETOOMANYREFS
    Errno::ESHUTDOWN
    Errno::ENOTCONN
    Errno::EISCONN
    Errno::ENOBUFS
    Errno::ECONNRESET
    Errno::ECONNABORTED
    Errno::ENETRESET
    Errno::ENETUNREACH
    Errno::ENETDOWN
    Errno::EADDRNOTAVAIL
    Errno::EADDRINUSE
    Errno::EAFNOSUPPORT
    Errno::EPFNOSUPPORT
    Errno::EOPNOTSUPP
    Errno::ESOCKTNOSUPPORT
    Errno::EPROTONOSUPPORT
    Errno::ENOPROTOOPT
    Errno::EPROTOTYPE
    Errno::EMSGSIZE
    Errno::EDESTADDRREQ
    Errno::ENOTSOCK
    Errno::EUSERS
    Errno::EILSEQ
    Errno::EOVERFLOW
    Errno::EBADMSG
    Errno::EMULTIHOP
    Errno::EPROTO
    Errno::ENOLINK
    Errno::EREMOTE
    Errno::ENOSR
    Errno::ETIME
    Errno::ENODATA
    Errno::ENOSTR
    Errno::EIDRM
    Errno::ENOMSG
    Errno::ELOOP
    Errno::ENOTEMPTY
    Errno::ENOSYS
    Errno::ENOLCK
    Errno::ENAMETOOLONG
    Errno::EDEADLK
    Errno::ERANGE
    Errno::EDOM
    Errno::EPIPE
    Errno::EMLINK
    Errno::EROFS
    Errno::ESPIPE
    Errno::ENOSPC
    Errno::EFBIG
    Errno::ETXTBSY
    Errno::ENOTTY
    Errno::EMFILE
    Errno::ENFILE
    Errno::EINVAL
    Errno::EISDIR
    Errno::ENOTDIR
    Errno::ENODEV
    Errno::EXDEV
    Errno::EEXIST
    Errno::EBUSY
    Errno::ENOTBLK
    Errno::EFAULT
    Errno::EACCES
    Errno::ENOMEM
    Errno::EAGAIN
    Errno::ECHILD
    Errno::EBADF
    Errno::ENOEXEC
    Errno::E2BIG
    Errno::ENXIO
    Errno::EIO
    Errno::EINTR
    Errno::ESRCH
    Errno::ENOENT
    Errno::EPERM
    Errno::NOERROR
  RangeError
    FloatDomainError
  ZeroDivisionError
  RuntimeError
    Psych::Error
      Psych::SyntaxError
    Gem::Exception
      Gem::VerificationError
      Gem::RemoteSourceException
      Gem::RemoteInstallationSkipped
      Gem::RemoteInstallationCancelled
      Gem::RemoteError
      Gem::OperationNotSupportedError
      Gem::InvalidSpecificationException
      Gem::InstallError
      Gem::GemNotFoundException
        Gem::SpecificGemNotFoundException
      Gem::FormatException
      Gem::FilePermissionError
      Gem::EndOfYAMLException
      Gem::DocumentError
      Gem::GemNotInHomeException
      Gem::DependencyRemovalException
      Gem::DependencyError
      Gem::CommandLineError
      Gem::RemoteFetcher::FetchError
        Gem::RemoteFetcher::UnknownHostError
    Timeout::Error
      Resolv::ResolvTimeout
    Psych::Exception
      Psych::BadAlias
    Logger::Error
      Logger::ShiftingError
    OptionParser::ParseError
      OptionParser::InvalidArgument
        OptionParser::AmbiguousArgument
      OptionParser::InvalidOption
      OptionParser::MissingArgument
      OptionParser::NeedlessArgument
      OptionParser::AmbiguousOption
  NameError
    NoMethodError
      ActiveModel::MissingAttributeError
      ActiveRecord::UnknownAttributeError
  ArgumentError
    Gem::Requirement::BadRequirementError
    I18n::ArgumentError
      I18n::UnknownFileType
      I18n::ReservedInterpolationKey
      I18n::MissingInterpolationArgument
      I18n::InvalidPluralizationData
      I18n::MissingTranslationData
      I18n::InvalidLocaleData
      I18n::InvalidLocale
    ActiveResource::MissingPrefixParam
  TypeError
  Hash::DisallowedType
  Bundler::MarshalError
  Bundler::InvalidSpecSet
  Bundler::BundlerError
    Bundler::VersionConflict
    Bundler::LockfileError
    Bundler::SecurityError
    Bundler::RubyVersionMismatch
    Bundler::HTTPError
    Bundler::ProductionError
    Bundler::InvalidOption
    Bundler::GemspecError
    Bundler::DeprecatedError
    Bundler::GitError
    Bundler::PathError
    Bundler::InstallHookError
    Bundler::InstallError
    Bundler::GemfileError
    Bundler::GemNotFound
    Bundler::GemfileNotFound
  TSort::Cyclic
  SocketError
  Racc::ParseError
  OpenSSL::OpenSSLError
    OpenSSL::SSL::Session::SessionError
    OpenSSL::SSL::SSLError
    OpenSSL::Random::RandomError
    OpenSSL::PKey::EC::Point::Error
    OpenSSL::PKey::EC::Group::Error
    OpenSSL::PKey::PKeyError
      OpenSSL::PKey::ECError
      OpenSSL::PKey::DHError
      OpenSSL::PKey::DSAError
      OpenSSL::PKey::RSAError
    OpenSSL::PKCS5::PKCS5Error
    OpenSSL::PKCS7::PKCS7Error
    OpenSSL::PKCS12::PKCS12Error
    OpenSSL::Netscape::SPKIError
    OpenSSL::HMACError
    OpenSSL::Digest::DigestError
    OpenSSL::ConfigError
    OpenSSL::Cipher::CipherError
    OpenSSL::BNError
    OpenSSL::OCSP::OCSPError
    OpenSSL::X509::StoreError
    OpenSSL::X509::RevokedError
    OpenSSL::X509::RequestError
    OpenSSL::X509::NameError
    OpenSSL::X509::ExtensionError
    OpenSSL::X509::CRLError
    OpenSSL::X509::CertificateError
    OpenSSL::X509::AttributeError
    OpenSSL::ASN1::ASN1Error
    OpenSSL::Engine::EngineError
  ExecJS::Error
    ExecJS::RuntimeError
      ExecJS::RuntimeUnavailable
    ExecJS::ProgramError
  StringScanner::Error
  URI::Error
    URI::BadURIError
    URI::InvalidComponentError
    URI::InvalidURIError
  JSON::JSONError
    JSON::MissingUnicodeSupport
    JSON::GeneratorError
    JSON::ParserError
      JSON::NestingError
        JSON::CircularDatastructure
  Resolv::DNS::EncodeError
  Resolv::DNS::DecodeError
  Resolv::ResolvError
    Resolv::DNS::Config::OtherResolvError
    Resolv::DNS::Config::NXDomain
  Resolv::DNS::Requester::RequestError
  Journey::Router::RoutingError
  MultiJson::LoadError
  ActionController::ActionControllerError
    ActionController::UnknownHttpMethod
    ActionController::SessionOverflowError
    ActionController::MissingFile
    ActionController::UnknownController
    ActionController::MethodNotAllowed
      ActionController::NotImplemented
    ActionController::RoutingError
    ActionController::RenderError
  Zlib::Error
    Zlib::VersionError
    Zlib::BufError
    Zlib::MemError
    Zlib::StreamError
    Zlib::DataError
    Zlib::NeedDict
    Zlib::StreamEnd
    Zlib::GzipFile::Error
      Zlib::GzipFile::LengthError
      Zlib::GzipFile::CRCError
      Zlib::GzipFile::NoFooter
  ActiveSupport::SafeBuffer::SafeConcatError
  ActiveResource::ConnectionError
    ActiveResource::ClientError
      ActiveResource::ResourceGone
      ActiveResource::ResourceConflict
      ActiveResource::ResourceNotFound
      ActiveResource::ForbiddenAccess
      ActiveResource::UnauthorizedAccess
      ActiveResource::BadRequest
      ActiveResource::MethodNotAllowed
    ActiveResource::Redirection
    ActiveResource::SSLError
    ActiveResource::TimeoutError
    ActiveResource::ServerError
  Sass::SyntaxError
    Sass::UnitConversionError
  TZInfo::NoOffsetsDefined
  TZInfo::UnknownTimezone
  TZInfo::InvalidTimezoneIdentifier
  TZInfo::PeriodNotFound
  TZInfo::AmbiguousTime
  TZInfo::InvalidCountryCode
  ActionDispatch::Cookies::CookieOverflow
  ActiveRecord::ActiveRecordError
    ActiveRecord::UnknownPrimaryKey
    ActiveRecord::MultiparameterAssignmentErrors
    ActiveRecord::AttributeAssignmentError
    ActiveRecord::DangerousAttributeError
    ActiveRecord::Rollback
    ActiveRecord::ReadOnlyRecord
    ActiveRecord::ConfigurationError
    ActiveRecord::StaleObjectError
    ActiveRecord::PreparedStatementInvalid
    ActiveRecord::StatementInvalid
      ActiveRecord::WrappedDatabaseException
        ActiveRecord::InvalidForeignKey
        ActiveRecord::RecordNotUnique
    ActiveRecord::ThrowResult
    ActiveRecord::RecordNotSaved
    ActiveRecord::RecordNotFound
    ActiveRecord::ConnectionNotEstablished
      ActiveRecord::ConnectionTimeoutError
    ActiveRecord::AdapterNotFound
    ActiveRecord::AdapterNotSpecified
    ActiveRecord::SerializationTypeMismatch
    ActiveRecord::AssociationTypeMismatch
    ActiveRecord::SubclassNotFound
    ActiveRecord::RecordInvalid
    ActiveRecord::DeleteRestrictionError
    ActiveRecord::ReadOnlyAssociation
    ActiveRecord::EagerLoadPolymorphicError
    ActiveRecord::HasAndBelongsToManyAssociationForeignKeyNeeded
    ActiveRecord::HasManyThroughNestedAssociationsAreReadonly
    ActiveRecord::HasManyThroughCantDissociateNewRecords
    ActiveRecord::HasManyThroughCantAssociateNewRecords
    ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection
    ActiveRecord::HasManyThroughSourceAssociationNotFoundError
    ActiveRecord::HasOneThroughCantAssociateThroughCollection
    ActiveRecord::HasManyThroughAssociationPointlessSourceTypeError
    ActiveRecord::HasManyThroughAssociationPolymorphicThroughError
    ActiveRecord::HasManyThroughAssociationPolymorphicSourceError
    ActiveRecord::HasManyThroughAssociationNotFoundError
    ActiveRecord::InverseOfAssociationNotFoundError
    ActiveRecord::NestedAttributes::TooManyRecords
    ActiveRecord::Transactions::TransactionError
  ActiveModel::MassAssignmentSecurity::Error
  ActiveModel::StrictValidationFailed
  ActiveSupport::JSON::Encoding::CircularReferenceError
  Sprockets::Error
    Sprockets::UnserializeError
    Sprockets::FileOutsidePaths
    Sprockets::FileNotFound
    Sprockets::EncodingError
    Sprockets::ContentTypeMismatch
    Sprockets::CircularDependencyError
    Sprockets::ArgumentError
  ActionDispatch::RemoteIp::IpSpoofAttackError
  ActionDispatch::Session::SessionRestoreError

Holy shit, such a long list.