Buffy vs. Faith - I love Faith, and while Buffy and Faith were definitely pretty evenly matched every single time they've actually fought, if we are talking season 7 Buffy vs Faith, she'd definitely win. Faith has some undeniable skill, but she's bound to be a tad rusty after being locked up with no demon/vampire slaying for all of that time.
Giles vs. Wesley Wyndam-Pryce - Wesley would win this one, but only by a hair, I think. Wesley goes to places in his normal persona that Giles would only go to in his Ripper persona, and there is his advantage. However, I will say that it seems likely that Giles in his Ripper persona would beat the pants off of Wes.
Angel vs. Spike - The only way I think Spike could win this one is by doing something underhanded. Angel has shown, throughout a total of 8 years (On the show, not counting comics. Don't read em,) that he is an AMAZING fighter. He's taken out more enemies over the years than Spike has, on both BtVS and Angel. The only way Spike, post ensoulment, could take out that demon in season 7 was by putting on his "big bad" persona, and it just seems to me that Angel doesn't need a persona to be a badass when it comes to the kick-o and fight-o, he already is one.
Dawn vs. Fred - Hmmm...Bit of an unfair match here, if you ask me. You've got Dawn, who has had the advantage of having a sister for a slayer and learning from her most of her life versus a book worm, who was mostly sheltered, before her situation in Pylea. Smarter, emotionally stronger? Fred, definitely. But if you pit them against one another in hand to hand combat, I gotta think the Slayers lil sis is gonna whoop her butt.
Cordelia (with demon powers) vs. Anya (with demon powers) - We never really saw Cordelia fight with her demon powers, so we don't really know how they work. Anya, on the other hand, we saw her fight with them on a few occasions, and she was quite strong.
Charles Gunn vs. Robin Wood - There was a thread about this a while back, and I have the same opinion of this as I did back then....Gunn, all the way. Robin Wood may have more technical knowledge, but it's quite obvious to me that he wasn't able to apply it much. Technical knowledge means little next to someone with YEARS of field experience. Book knowledge<field experience almost every time.
Tara vs. Connor - Not even a contest. I don't think Tara was ever that powerful of a witch, so I don't think she'd be able to do much with magic against Connor. Connor, much as the little brat annoys me, was an amazing fighter with massive amounts of strength. He would rip Tara apart.
Xander vs. Lorne - Possibly the one and ONLY reason for this is because Lorne is more of a lover than a fighter.
Vampire Willow vs. Doyle - Definitely Vamp Will on this one. Doyle may have been a half demon, but he showed on several occasions that he just wasn't that strong, and that he wasn't really a great fighter. His main purpose was the visions, he was never really meant for 'field work,' I don't think. Vamp Will had to be a strong vamp, as she obviously had to do SOMETHING to get to being the Masters right hand. She'd eat Doyle for breakfast.