In today's review of GI Joe: Retaliation Firefly, Monkey Boy said that this was the first time there's been an unmasked 3¾" Firefly. However, that doesn't mean this is the first time there's ever been an unmasked Firefly.
For instance, perhaps you'll recall Sigma 6 Firefly, who was released in 2006:
Nice, nice. But if you're feeling charitable, how about this 12" Firefly from 2002? He's definitely showing a lot more face than any previous version:
But even that one isn't the first first time Firefly's face was seen. See, in an issue of the GI Joe comic, Firefly takes off his mask on-panel, becoming the final major "masked" character to be revealed: he unmasked in #126, Destro lost the bucket in #97 (1990), Snake-Eyes in #93, Zartan in #84 (both 1989), Cobra Commander way back in #55 (1987), and Storm Shadow in #52 (1986).
Anyway, back on topic. In 1992, Firefly took off his mask for the first time: