My top 5 (in no particular order)
Death Marshal - Although I hardly ever take more than 1, I think you should always consider a Death Marshal because Pine box can win games. particularly effective against Wp 5 masters/henchmen (Lilith / McMourning / Sebastian)
Guild Austringer - Ability to terrorize totems and small scheme running models along with the ability to cause your opponents to discard cards, or deliver orders to push your models around (often to move out of combat) and then do interact actions will nearly always enable get you VP from unusual situations.
Guild Pathfinder & Traps - This model will ask questions for your opponent, He and his traps have to be dealt with or they can lock down big areas of the board with their 2" melee which of course denies Interacts, attacks and charges. The Pathfinder itself has a pretty good gun with 2 excellent triggers.
Watcher - Flight, Armour 1, Stubborn, Wk 6 = One of the better scheme runners in the game period. The cover removal is also very good.
Witchling Stalker- Cheap Condition removal along with high (and accurate) damage output, Nothing more to be said that hasnt been covered by others
(Honourable mentions to: Abuela, Francisco, Papa Loco, The Judge, Guild Riflemen, The Peacekeeper, Samael Hopkins and Pistolero De Latigo)