Glass Cannon

Glass Cannon is a bit of gaming slang that refers to an archetypical character focused heavily on offense at the expense of defense. Basically, the character can hit with incredible force, and will usually wreck, or at least seriously maim, any foe that it hits, but it folds like a wet napkin if anybody hits it in turn.

Not to be confused with the Fragile Speedster, who hits fast and repeatedly as opposed to hitting hard, but risks folding similarly if hit.

In /tg/

The Wizard, Sorcerer and Warlock of Dungeons & Dragons can dish out large amounts of damage and debilitation with their spells, but are traditionally restricted to the lightest armor and have the lowest innate hit points score, so they cannot take a lot of damage.

The Rogue, similarly, can dish out large amounts of damage with its Sneak Attack/Backstab mechanic, but it is the least-armored of the martial classes and has the lowest amount of hit points.

In Warhammer 40,000, the Eldar and Dark Eldar factions tend to have multiple attacks, high weapon skill, and good armor penetration with both melee and ranged weapons, meaning they will frequently kill any human-equivalent creature they fight. However, their toughness is below par, so if hit in return, they will usually die quickly. Similarly, the Tau have some of the most potent firepower in the game, but their poor melee weapon skill means they will be swiftly overrun if enemy units make it into melee with them.