Star Wars: Knights of the Old Republic/Pazaak

Pazaak is a card game resembling Blackjack. Playing is optional, but it can be a good way to get credits (particularly for light side characters) and some other rewards.

Pazaak Rules
This is activated when you acquire a Pazaak deck from one of the following characters:

Since some characters can be persuaded using skill or the Force to give you a Pazaak deck for free, there's no real need to buy one on Taris (50 credits may be a trifling sum, but so are the amounts you can wager there).

This 'quest' is completed when you play a game of Pazaak for a wager, although you receive no experience for doing so. However, before wagering you should really acquire better cards for your side deck, since the only available cards from which to choose initially are two of each from +1 to +5. Obviously and ideally, you want a side deck of ten +/- cards, some of which can be purchased from merchants:

Cost gives some indication of the usefulness of each card, although with your initial side deck you shouldn't waste credits on + cards (with the possible exception of +6, although there are obviously much better cards).

Igear sells for 25% less, Mika Dorin for 50% more (but he can only do so once you escape the Leviathan, having been brought on board after leaving the planet on which you found a fourth Star Map). Cards can also be acquired for free elsewhere (after leaving Taris, this is usually via a final wager after defeating your opponents a certain number of times):

You can replace your entire initial side deck of + cards with the equivalent +/- cards before leaving Dantooine, giving you a much better chance of winning.

Niklos
Once you've defeated him five more times than he's defeated you, he accuses you of cheating and will no longer play (if you play a consecutive game after this occurs then he doesn't accuse you until it has been played, regardless of the result):

Fortunately there's still Gelrood...

Gelrood
Otherwise:

Sol'aa
Maximum Wager: 120 (5 wins)
 * Jedi Enclave

Kudos
Maximum Wager: 75 (4 wins) | 200 (4 wins) | 50 (2 wins)
 * Hunter's Lodge

Furko Nellis
Maximum Wager: 50 | 200 | 500
 * Cantina

Fodo Medoo
Maximum Wager: 75 (4 wins) | 200 (4 wins) | 600 (1 win)
 * Czerka Landing Port

Jolan Aphett
Maximum Wager: 200 (10 wins)
 * West Central

Gonto Yas
Maximum Wager: 200 (10 wins)
 * Ahto West

Gonto Yas
Otherwise After 10 Wins:

Toll Apkar
Maximum Wager: 100
 * Dreshdae

Suvam Tan
Maximum Wager: 750 (10 wins)
 * Yavin Station