Friend playing an Artificer, what's a good class/build to duo with?

[Apoxia]

Maybe a single class Monk is the way to go...here's a quick mock-up...hows it look

Halfling Monk 20 "Ninja Spy'

Str 10
Dex 16
Con 12
Int 10
Wis 18 (LvL ups here)
Cha 8 

1 Toughness
1M TWF
2M Stunning Fist
3 Weapon Finesse
3M Dark Path
6 Power Attack
6M Dodge
9 ITWF
12 IC:Bludgeon
15 GTWF
18 Need Suggestion!?!
ED GMoF
21 Vorpal Strikes or Improved Martial Arts
24 Vorpal Strikes or Improved Martial Arts

Skills: Balance, Concen, Spot, UMD

Does it need to be halfling? If you have Helf its by far a better option. Since you didn't split str and dex and went pure dex/con/wis you have to spend the extra feat on finnesse, which means that you can't take both cleaves (which is what i would have suggested as your extra feat). Since you arent getting cleaves to go with your power attack, have you considered dropping it for precision? It gives you a nice bonus to attack but also bypasses 25% fort, which is very nice.

[Kilbar]

Maybe a single class Monk is the way to go...here's a quick mock-up...hows it look

Halfling Monk 20 "Ninja Spy'

Str 10
Dex 16
Con 12
Int 10
Wis 18 (LvL ups here)
Cha 8 

1 Toughness
1M TWF
2M Stunning Fist
3 Weapon Finesse
3M Dark Path
6 Power Attack
6M Dodge
9 ITWF
12 IC:Bludgeon
15 GTWF
18 Need Suggestion!?!
ED GMoF
21 Vorpal Strikes or Improved Martial Arts
24 Vorpal Strikes or Improved Martial Arts

Skills: Balance, Concen, Spot, UMD

For this build, I recommend Resilience at 18th level for a +4 saves toggle. You'll need to pick and choose when to use it, however, as it would be mutually exclusive with Power Attack stance. Another choice is Luck of Heroes for +1 to all saves with no need to go into a stance.

[Failedlegend]

No halfling isn't required its just the only race without -2 Con that has +Dex and 32pt. making it easier to make Pre-Req for I/GTWF...as for Cleave & Great Cleave does that even work fir unarmed I could have sworn it was buggy and the range was really short or something

[Apoxia]

No halfling isn't required its just the only race without -2 Con that has +Dex and 32pt. making it easier to make Pre-Req for I/GTWF...as for Cleave & Great Cleave does that even work fir unarmed I could have sworn it was buggy and the range was really short or something

The only concern I see with halfling and your build is lack of later level sustain. Potions work fine through much of the early leveling process but you may find it lacking as a dark monk past 13-14. Your UMD wont be high enough as a non class skill for heal scrolls which is why I mentioned Helf for the cleric dilly. You get the human stat enhancements as well which helps make up for not going halfling somewhat as well, not to mention access to the human improved recovery line (heal amp) which is bread and butter for any monk.

Do you have access to any tomes?

If you want to stay halfling I would reccommend going light. You will do less dps but it would help mitigate the lack of sustain as well as give you access to a lot of DR bypass, which will mean keeping less situational wraps on hand.

In regards to Cleaves, they function fine on unarmed and have the proper radius / attack range ATM. There is a bug with cleave on Elves (M/F) Human (F) and possibly one other race im forgetting (But is unaffected by Helf or Halfling) that causes a whirlwind attack windup animation to occur before the cleave resulting in a pause between activation and attack, which while annoying and at first glance considered a loss of dps, actually is a major boon to you. The windup bug actually allows you to activate another non animation attack ability in unison with the cleave before it hits causing the non animation ability (ToD, SF, Void Strike) to cleave to everything. You now have an aoe stun, overpowered huh?

[Failedlegend]

The only concern I see with halfling and your build is lack of later level sustain. Potions work fine through much of the early leveling process but you may find it lacking as a dark monk past 13-14. Your UMD wont be high enough as a non class skill for heal scrolls which is why I mentioned Helf for the cleric dilly. You get the human stat enhancements as well which helps make up for not going halfling somewhat as well, not to mention access to the human improved recovery line (heal amp) which is bread and butter for any monk.5

Do you have access to any tomes?

If you want to stay halfling I would reccommend going light. You will do less dps but it would help mitigate the lack of sustain as well as give you access to a lot of DR bypass, which will mean keeping less situational wraps on hand.

In regards to Cleaves, they function fine on unarmed and have the proper radius / attack range ATM. There is a bug with cleave on Elves (M/F) Human (F) and possibly one other race im forgetting (But is unaffected by Helf or Halfling) that causes a whirlwind attack windup animation to occur before the cleave resulting in a pause between activation and attack, which while annoying and at first glance considered a loss of dps, actually is a major boon to you. The windup bug actually allows you to activate another non animation attack ability in unison with the cleave before it hits causing the non animation ability (ToD, SF, Void Strike) to cleave to everything. You now have an aoe stun, overpowered huh?

Ah so there is a bug but it's irrelevant if I go HE ok...and it seems with Cleric Dilly I'll have 95% chance to use heals scrolls at lvl 15+ and if I somehow get enough UMD I'll swap it rogue dilly or something.

Note: I may switch to Light Monk at some point I just want to try out Dark Monk

Half-Elf Monk 20 "Ninja Spy'

Str 14
Dex 16
Con 12
Int 10
Wis 16 (LvL ups here)
Cha 8 

1 Toughness
1D Cleric
1M TWF
2M Stunning Fist
3 Power Attack
3M Dark Path
6 Cleave
6M Dodge
9 ITWF
12 IC:Bludgeon
15 GTWF
18 Great Cleave
ED GMoF
21 Vorpal Strikes or Improved Martial Arts
24 Improved Martial Arts or Vorpal Strikes

Skills: Balance, Concen, Spot, UMD

[Apoxia]

Ah so there is a bug but it's irrelevant if I go HE ok...and it seems with Cleric Dilly I'll have 95% chance to use heals scrolls at lvl 15+ and if I somehow get enough UMD I'll swap it rogue dilly or something.

Note: I may switch to Light Monk at some point I just want to try out Dark Monk

Half-Elf Monk 20 "Ninja Spy'

Str 14
Dex 16
Con 12
Int 10
Wis 16 (LvL ups here)
Cha 8 

1 Toughness
1D Cleric
1M TWF
2M Stunning Fist
3 Power Attack
3M Dark Path
6 Cleave
6M Dodge
9 ITWF
12 IC:Bludgeon
15 GTWF
18 Great Cleave
ED GMoF
21 Vorpal Strikes or Improved Martial Arts
24 Improved Martial Arts or Vorpal Strikes

Skills: Balance, Concen, Spot, UMD

Looks pretty solid. Even with the CON a little low you should end up around 550-600 hp in GMOF once you get decently geared. Have fun breezing through content, esp. with free DR bypasses from your Arti friend!