Pit
"Pit" is a card game for three to eight players that is based on the commodities market. Players try to get as many cards of the same commodity as possible. Trading cards is completely done through negotiation. Players announce how many cards of a certain commodity they are willing to trade, and other players offer an equal number of cards of different commodities. The round continues until nobody is willing to trade with another player. At that point scoring is completed based on the type of commodity each player has and the number of cards of that commodity based on a chart in the rules.
I'm The Boss
"I'm the Boss" is a game that was developed by Sid Sackson in the early 1990s. Players compete to negotiate their way into being part of the division of one of the 16 deals on the game board. Each deal is a different amount of money. One player that plays the boss card is in charge of how much each player gets. Only players that agree to that division can play a card and get part of the money in the deal. The boss has to be careful though, because one of the members that agree to the deal might play a card to cut him (the boss) or another player out of the deal or become the boss himself. If you make enemies in this negotiation game, it can cost you later on in the big deals when those players play cards to cut you out.
Diplomacy
"Diplomacy" is a classic game from the 1950s, but is still listed as one of the top negotiation games on the list from TheDiceTower.com website. A game doesn't remain on that list after this many years without some intrigue and of course backstabbing potential. "Diplomacy" is a game for two to seven players, with a setting in Europe just before World War I. Players control the seven world powers at that time, working to get support from each other to win the most battles. Alliances can be negotiated and changed throughout the game. To win, you must be able to negotiate the best alliances to protect your army at any specific time during the game. Your ally at one time during the game will likely be your enemy later.
Partner Poker
In the game of partner poker, you must decide to play for the pot alone or try to team up with one other player at the table to split the pot if you win. Each player puts an equal amount of money into the pot to start the game and receives three cards. Any player wanting to try to "partner up" then announces his highest card. Starting with the player to the left of the dealer, play rotates clockwise with each player either saying he will "go it alone" or ask another player to partner up. If two players agree to be partners, their six cards are combined for one hand. Anyone who does not partner up gets four new cards. The player or pair with the highest ranking hand wins the pot. If it's a pair, they split it evenly.