Terran Heroes
Jim Raynor
Perhaps the most important Terran leader, Raynor leads a militia/terrorist group called Raynor's Raiders, which strikes an alliance with an even more terrorizing group, the Sons of Korhal, in Episode 1 and continues to both help and fight against Terrans, Protoss, and Zerg forces through the rest of StarCraft and Broodwar.
Jim is StarCraft's ideal of a resourceful, understanding, and at times empathic hero: one who can create an army from the militia of Mar Sara and Antiga Prime; who understands what others are thinking and can work well with them; and who responds as players do to events despite his taxing experiences. He also symbolizes the slight love (in his case, for Sarah Kerrigan) that Blizzard Entertainment provides in the storyline. StarCraft is above all Raynor's story, as he somehow appears in each episode to some significant extent; it is the story of Raynor's meeting with Sarah Kerrigan, loss of her, wars against her, and possibly--that would be a logical progression--reunion with her in StarCraft 2. He is also very sensible, fighting when necessary but retreating when he must, allying with others to what he considers would do him the most good, and forming alliances with the natural partners of the Terrans, the Protoss, through much of BroodWar.
Duran
The inexplicable Duran seems to "Serve a greater power", by which he most likely refers to the Xel'Nagan legacy or the Overmind's legacy; he seems both separate from the Zerg and its goals and yet immersed in his attempt to create the Hybrid, a blend between Zerg and Protoss to finally unite the purities of form and essence. His attempt to destroy the UED can be seen as a way of fulfilling his goals, although we must look to StarCraft 2 to see how his creations play into the game.