Doom Troopers fire effect
Doom Troopers has a cool fire effect on the title screen:
The effect is surprisingly simple: the foreground is high priority plane A (plane B is not used), with the Doom Troopers logo being transparent. The fire is low priority sprites (showing through the gaps)…
…and in particular, they're the explosions used through the game, spawning at random locations behind the title logo. They only show through the gaps making it hard to tell their shape, which is why they look like fire.