The full-featured ESP8266 flashing tool for Tasmota. With the great ESPtool from Espressif under the hood, and all required settings by default.

Features

Automatic backup of current ESP image before flashing: in case you want to return to manufacturer firmware
Now supporting backup sizes up to 16MB
Flash local .bin images, or simply select from release or development images: it will download them automatically
Send configuration to flashed device via serial: one-click configure of Wifi (including recovery AP), MQTT, Module and/or Template
Single-click get the IP of your device (DISCLAIMER: this functionality depends on the current state of your device, so it might require a few tries to get the proper result)
Dark theme: proven to increase flashing speed and reliability

Installation and how to run

Option 1: get Windows standalone executable (thanks @Jason2866):
tasmotizer.exe (64bit)
tasmotizer-x86.exe (32bit)
In the odd case of your antivirus going haywire over that application, it's a false positive.
Option 2: Install from PyPI using pip:
Upgrade pip and wheel packages: pip3 install --upgrade pip wheel
Install tasmotizer: pip3 install tasmotizer
Then simply run tasmotizer.py or python3 -m tasmotizer.py from the shell/command line
Option 3: Build from source
Clone the repo
Upgrade pip and wheel packages: pip3 install --upgrade pip wheel
Install requirements pip3 install -r requirements.txt
Run python3 tasmotizer.py and flash away!