Two-Face's Coin

Two-Face's Coin is a rare, double-headed silver American dollar used by Two-Face to decide significant decisions on whether he should be virtuous and merciful or criminal and relentless.

History
The two-headed coin was originally one of many which belonged to Harvey’s father, Christopher Dent; an alcoholic who would use the coin to psychologically and physically abuse Harvey; subjecting his son to a cruel game of "flipping the coin" on wether or not Harvey would be beaten. However, as Christopher always chose "heads" and Harvey, not knowing the the coin was double-sided, always chose "tails", Harvey always lost and get savagely beaten.

As a sign of love years later, Christopher, now a derelict drunk living in a run-down apartment with no memory of the “game” or his abuse, gave Harvey the coin as a gift; revealing to Harvey the game's injustice. Keeping the coin, Harvey quickly developed a habit of flipping the coin idly, especially when he became agitated. During the trial of crime boss Maroni, the acid that the mobster threw at Dent also hit the coin in his pocket; scarring the exposed side. Dent used the coin's newly-given duality as the tie-breaker between his warring desires between light and dark. Following an initial rampage through Gotham, dealing justice as dictated by the coin, Dent finally confronted his father, he played the “game” with the new coin, however, as "Good Heads" came up, Two-Face let the old man live.

Trivia

 * Two-Face's coin first appeared in Detective Comics #66 (August, 1942)
 * At one point, Two-Face was so dependent on the coin for any of his criminal acts that he could be easily defeated by taking the coin away from him or preventing him from seeing the result of the flip. Following psycological therapy, Dent has since lessened his dependency on the coin flip to whether a situation should be implemented, rather than each individual act.
 * Dent's coin is genuinely silver, as evidenced by one occasion when Two-Face used the coin to kill a werewolf.