You could have a guy you're fighting shout "Hey, Moron... That fire skill won't work on me!" if he's hit with one.
That was done, even in movies.
stupid movie
Hostage and Hero duck behind a metal desk. Hostage sees the hero has a couple of grenades hanging off his belt. Hostage grabs one and quickly tosses it at the terrorist.
Terrorist looks... bends down... and picks up the grenade.
Terrorist: Hey, moron. You forgot to take the pin out.
Hero is surprised at the comment. Quickly checks... yep, one grenade is missing. He glares at the hostage, grabs the other... pulls the pin... and tosses the other at the terrorist.
The terrorist, about to take a step forward, suddenly sees the second grenade, and goes pale.
BOOM!
Up is down, left is right and sideways is straight ahead. - Cord "Circle of Iron", 1978 (written by Bruce Lee and James Coburn... really...)