STM32L476G discovery kit is best for ultra low power embedded application, featuring STM32L4 ULP series MCU incorporating ARM Cortex M4 core.
The STM32L476G discovery kit explores both develop and share the STM32L4 ULP embedded application to make use of LCD, LEDs, Audio DAC, ST MEMS Sensors including (digital microphone, Accelerometer, Gyroscope, magnetometer), joystick and USB-OTG.
Along with this the STM32L476 is also equipped with 128Mbit Quad SPI Flash memory.
Not to say much about power features, the STM32L4 series provides unmatched Ultra-Low power features, also the on board embedded ammeter is also provided to measure the CPU’s power consumption in Low Power Mode.
The STM32L476G discovery board explores STM32L476VGT6 microcontroller,coupled with 1-Mbyte Flash memory, 128 Kbyte RAM in an LQFP100 package. With on board ST-Link debugger/programmer with a separate selection-mode switch which enables the board to be used as a standalone ST-LINK/V2-1. The board has three functionality USB support: Virtual COM port, mass storage, debug port. A separate USB-OTG FS with Micro-AB is also provided for further debugging of the board.
STM32L4 discovery kit also expands the possibility for integrating other technology board into the current version of the board via expansion and probing connectivity. For easy software development, user can look for online tool with a support of Mbed online tools facility.Comprehensive free software including a variety of examples, part of STM32Cube package.
Features:

STM32L476VGT6 microcontroller featuring 1 Mbyte of Flash memory, 128 Kbytes of RAM in LQFP100 package
On-board ST-LINK/V2-1 supporting USB re-enumeration capability
Three different interfaces supported on USB:

Virtual com port
Mass storage
Debug port

Mbed-enabled (mbed.org)
LCD 24 segments, 4 commons in DIP 28 package
Seven LEDs:

LD1 (red/green) for USB communication
LD2 (red) for 3.3 V power on
LD3 Overcurrent (red)
LD4 (red), LD5 (green) two user LEDs
LD6 (green), LD7 (red) USB OTG FS LEDs

Pushbutton (reset)
Four directions Joystick with selection
USB OTG FS with micro-AB connector
SAI Audio DAC, Stereo with output jack
Digital Microphone MEMS Accelerometer and magnetometer Mems
Gyroscope MEMS
128-Mbit Quad-SPI Flash memory
MCU current ammeter with 4 ranges and auto calibration
Connector for external board or RF-EEPROM
Four power supply options:

ST-LINK/V2-1
USB FS connector
External 5 V
CR2032 battery (not provided)

Extension connectors
Comprehensive free software including a variety of examples, part of STM32Cube package

Relevant Resources:
Discovery kit with STM32L476VG MCU
STM32L476VG Discovery Kit