Chanuka - Dreidels & Cards
The dreidel is, of course, the four-sided top which has become almost synonymous with Chanuka. It is believed that playing dreidel likely began in response to the evil Greek decree which completely banned all Torah study. Not surprisingly, this decree was ignored by Torah scholars. When the Greek soldiers were seen approaching the schools and other centers of Torah study to carry out their inspections, the students would quickly hide their books and take out their dreidels in order to fool the soldiers into believing that only games were taking place.
The rules of the dreidel game require each player to contribute a number of coins to a central fund, the proceeds of which are used to pay out the winners. On each of the four sides of the dreidel appears one of the following letters: nun, gimmel, hey, and shin. The letters of the dreidel are said to represent the first letter of a different Yiddish word. The nun stands for the word "nisht", nothing, gimmel for "gantz", all, hey for "halb", half, and shin for "shtel", pay. After the dreidel ceases to spin and lands on one of its sides the letters serve to instruct the one whose turn it is how to proceed. For example, if the dreidel lands on the letter "hey" the player wins half the money which is currently in the pot, and so on. Although the dreidel game is essentially a form of gambling, it is generally considered to be a permissible form of gambling due to its simplicity and the insignificant amounts of money that are commonly used. Nevertheless, there have been a number of authorities in the past who opposed playing dreidel unconditionally and anything else that resembled gambling.
In addition to the gaming aspect for which the four letters of the dreidel are utilized, there are a number of other interpretations to the meaning of these letters, as well. The letters are widely believed to be an acronym for the words "nes gadol haya sham", meaning "a great miracle happened there." Another explanation offered is that the four letters of the dreidel represent the four spiritual elements that are found in every person: body, soul, intellect, and what is referred to as the "supreme encompassing strength". It is also noted that the gematria of the four letters equal that of "mashiach". Some sources claim that the original custom was to use wooden or silver dreidels.
Closely related to the custom of playing dreidel on Chanuka is that of playing cards. Playing cards on Chanuka likely become popular due to an ancient and lesser-known rabbinic decree which completely forbids playing cards except on days on which tachanun is not recited, in which case it is permitted. Since Chanuka offered an extended break from tachanun many individuals took the opportunity to spend much of their free time on Chanuka playing cards. It is also suggested that playing cards on Chanuka was popularized in an effort to ensure that the children would keep themselves occupied so that they remain awake until the family gathered to light the menora which often took place well into the night. In some communities playing with cards was an activity that was strictly restricted to Chanuka and Purim.
Many authorities in the past opposed card games without exception and tried to eliminate the practice entirely. According to Rabbi Levi Yitzchak of Berditchev, the playing-cards are imbued with a spirit of impurity which must be vigorously avoided. It is also noted that the gematria of "cards" is "Satan". Even a number of contemporary authorities maintain that the custom of playing cards on Chanuka should be abandoned as it is can lead to gambling, theft, and other possible prohibitions.
Another reason for the opposition to playing cards on Chanuka was because the card games were often played by the light of the Chanuka candles. This is in violation of the well-known halacha that one is forbidden to engage in any activity by the light of the Chanuka candles or to benefit from them in any way. As we recite as part of the candle lighting ceremony: "…During all eight days of Chanukah the candles we have kindled are holy and we are not permitted to make any use of them except to gaze upon them in order to praise Your great Name for Your miracles, Your wonders and Your salvations."
Nevertheless, although at one time card games may have been excessive and possibly impacted negatively on people's personal and professional lives, this is no longer the case today. As such, one who feels the need to play cards on an occasional basis, rather than engage in other unproductive pursuits, is permitted to do so. However, one who is able to engage in Torah study and other praiseworthy activities should certainly do so instead. 
 Otzar Kol Minhagei Yeshurun 19:4; Divrei Yatziv, OC 2:283.
 Nitei Gavriel, Hilchot Chanuka 51:3.
 Most Israeli dreidels replace the "shin" with a "peh", which represents the word "po", meaning "a great miracle happened here".
 Bnei Yissaschar 2:25, cited in Minhag Yisrael Torah, OC 670:5.
 Mahari Bruna 136.
 Minhag Yisrael Torah, OC 670:6.
 Noheg K'tzon Yosef p.188.
 Chavot Yair 126.
 Minhag Yisrael Torah, OC 670:7.
 Aruch Hashulchan, OC 670:9.
 Salmat Chaim 2:48,49. See also Rema, OC 547:12; Darkei Moshe, OC 639.
 Lehorot Natan 4:46; Igrot Sofrim, Chatam Sofer 3.