I won't bother posting the whole build because plenty of folks have done the knifemaster/scout route before -- including in this thread, but I think mine is fun to play without being gimped:
Lv.1 (R1): TWF/Weapon Finesse
Lv.2 (R2): Weapon Focus: Dagger
Lv.3 (R3): Shadow Strike
Lv.4 (R4): Offensive Defense
Lv.5 (F1): Combat Expertise/Gang Up
Lv.6 (F2): Agile Maneuvers
Lv.7 (R5): Improved Dirty Trick
Lv.8 (R6): Pressure Points/Underhanded
Lv.9 (R7): Greater Dirty Trick
The fighter dip is pretty obvious for keeping that BAB up, getting feats and helping with maneuvers. Weapon Finesse can be dropped too, for a brute build -- which actually helps circumvent the DR problem with daggers.
I thought of doing a Close Quarters Thrower/False Opening thing too, maybe someday.
Anyway, not terribly different than other builds, but the dirty tricks keep it fresh as long you're creative.
This is, of course, somewhat dependent on your GM to really be fun, but for a true dirty fighting scoundrel it can be super entertaining.