Most people have greater "push" strength than they do "pull" strength. I.e. most people can Bench more than they can row, and do more pushups than inverted rows. All exercises in this complex work the lats, biceps, and core.
The following three excercise are ways to build pull strength while challenging your core.
1. TRX assisted inverted row w/feet elevated.
Slight pause at the top of the movement. Its extremely important to not let your hips collapse, something that @Dion always emphasized to me.
2. Resistance band row w/plank, feet elevated.
A nice combination of strength, core engagement, and balance.
3. L-ish shaped pullups.
A way to engage the core and ab muscles during the pullup.