Love this thing to bits. I think two of the best partners would be:
SD/NP - Infernape- has similar speed and reactions to passive damage, and it can counter some of Ape's counters... it could be very effective.
NP - Mismagius- perfect defensive synergy (typing), with similar defenses and identical speed. Not completely identical for passive damage, but fairly close. Not quite as synergetic as Ape on an offensive front, but better from a defensive perspective.
Aside from those two, many of the best would likely require additional support, such as spinners. In particular, someone like Dragonite would work both defensively and offensively. Dragonite provides the fighting and bug resistance illusion, whilst Zoroark clears bulky waters and steels with Grass Knot and a fire move.
I haven't really looked too much at this gen's additions, but there's sure to be a couple of gems there!