Burning heretics is a classic move since... well... just about forever. However, in the far-off future of the 41st millennium, they don't just tie someone to a stake and light a pyre. They take the pyre with them using the Pyreblaster. Check out this new 40k weapon in this preview.
From the article:
The rumours have been circulating for a while now. But with the codex supplement announced on our road map and new cover art revealed, the fervent prayers of the faithful have been heard – the Black Templars are on their way.
What’s more, they’re bringing some shiny heretic-purging wargear with which to immolate anyone foolish enough to besmirch the glorious name of the God-Emperor. Behold the Primaris Initiate with pyreblaster!