From the original launch of CoH through at least a few issues later, Smoke Grenade from Devices debuffed enemy accuracy by many times more than intended due to a decimal place error in the powers data. Throwing one smoke grenade would typically reduce all enemies' chance to hit down to the 5% floor.
This was popularized during issue 0 by a guide on the forums, which if I recall correctly was called something like "Fire/Dev - level 40 in 4 weeks" (the level cap was 40 before issue 1). Fire was the best AoE set and /Dev was as good as being defense capped, so this was really easy to level at a time when leveling was definitely not easy. Despite the popularity of this guide, Smoke Grenade went unfixed for many months.