My first time in BG 1 started with the classic n00b party, Imoen, Montaron, Xzar, Khalid and Jaheira. Monty and Xzar eventually left, so I replaced them with Minsc, who went berserk and had to be put down, so I eventually ended up with Kivan and Xan.
Since then I've done a ton of playthroughs of both games. I've done the canon party a couple of times, once with vanilla and then once with the NPC mod; I've done an evil playthrough of both games as well and am in the middle of a second evil playthrough of the first game. First BG1 was Assassin NPC, Kagain, Shar-Teel, Viccy, Edwin, and Eldoth (who replaced Imoen). That party was a lot of fun. My rep was pretty low, but knocking over Baldur's Gate was a blast. Kagain, Viccy and Edwin are obviously all excellent NPCs, Shar-Teel's no slouch either (thanks to the magic of Tutu and dual-wielding), and Eldoth, despite some crappy stats, doesn't make too bad of an archer, especially against mages. Second evil group has Xzar, Monty and Tiax so far, I believe (using the NPC mod). Tiax sucks but is a lot of fun. Xzar has the unfortunate honour of being "That Mage Who's Not As Good As Edwin," but Monty is pretty impressive so far, I'm liking having him around. Give him some points in stealth and have him scout and backstab, or throw some plate on him and send him to the front lines, or give him a bow and have him decimate from the rear. Very versatile fellow.
Thanks to the NPC mod allowing me to have late game NPCs spawn outside of BG, I'm kind of tempted to make a Late Game NPC playthrough - Tiax, Quayle, Eldoth, Skie and Alora. That would be an interesting combination. A power-gamer's nightmare, but whatever.
Also, maybe an Archery group. Imoen, Kivan, Coran, Montaron, Eldoth, capped with an Archer CHARNAME.