Haley vs Penny= I would have to say it would be a draw because they probably would both use some sort of dirty fighting skills. I mean, hell, Pam is so hard on Penny that she most likely had to have some sort of defense in case things got hairy. Haley on the other hand would probably use dirty fighting (kicking, clawing, throwing items) so yeah, a draw.
Elliot vs Harvey= I would say Elliot. I think Harvey is too much of a pacifist to fight. that or he'd throw the fight so he could get out of it.
Shane vs Sam= If they are both sober, then Sam. If Shane is drunk and angry, then Shane. but in general, since Shane is mostly drunk, I would say Shane.
Lewis vs Willy= Willy's arms are probably very strong from reigning in fish all day, plus he has most likely been in some brawls in his heyday.
Clint vs Gunther= Clint, they work with a hammer and probably have very strong-arm muscles
Emily vs Leah= Leah, she carves wood, she probably would be good in hand to hand if she had a knife. (also, Emily is definitely a pacifist)
Alex vs Sebastian= Alex, Dude got football arms. he can probably tackle Seb and overpower
Abigail vs Maru= Abigail. she fights monsters and goes in the mines. Maru may have the upper hand on strategy, but Abigail has the upper hand on the offensive side
Jodi vs Caroline= They're too good of friends to try and fight each other.
Pam vs Marnie= the angry alcoholic people always win, at least from what I've seen
Linus vs Wizard= Linus has been living off the land for probably years, so he is probably able to defend himself from those wishing him harm because he's so self-sufficient
Demetrius vs Gus= Neither, they'd probably just end up talking about molecular gastronomy or something.
Morris vs Pierre= We all know this ended ;)
Kent vs Marlon= Marlon would win if he could use his sword, But Kent would definitely win in hand-to-hand combat
Sandy vs Robin= Robin. I mean, can she use her axe? even if she can't use it, she has the same advantage as Willy with her arm strength.
Vincent vs Leo= Leo and Vincent would only fight each other if they couldn't share, so in that case, penny wins because she breaks them up and makes them apologize. XD