Over multiple playthroughs, I've used some combos that seem to work quite well and thought to list them and their uses. Most of these combos require certain feats and a heavily psi-oriented build to be able to pull off such as Premeditation (50% psi cost reduction and 100% AP cost reduction) and Locus of Control (adds AOE affect to thought control psi abilities). Other helpful feats include Tranquility (5 point psi cost reduction when at full health), Neurology (up to 15 bonus to max psi points on headbands you craft), and Meditation (25 bonus to max psi), but a larger psi cost reduction can be achieved though crafting psi headbands.
Group combos:
Premeditation->Locus of Control->Enrage
Just this start alone can wreck groups of enemies since the affected ones tend to attack targets close to them and other unaffected enemies attack the affected enemies.
Premeditation->Locus of Control->Enrage->Thermodynamic Destabilization/Electrokinesis
Why not follow up a chaotic start with more chaos? Add an explosive finish or whittle down enemies to a quicker demise.
Premeditation->Locus of Control->Bilocation
If you're in a decent defensive position with a bottleneck, this works well to clog it up while enemies get whittled down by their doppelgangers which happily ignore pesky shields as a bonus.
Premeditation->Locus of Control->Psi-cognitive Interruption
When facing a Psi-heavy group of Lunatics, this can stall their relentless barrage of Psi abilities while doing a good chunk of damage.
Premeditation->Locus of Control->Neural Overload
Up against a group of shielded enemies? Try this for decent AOE damage that bypasses shields.
Single enemy combo:
Premeditation->Mental Breakdown->Bilocation->Cryo-Shield/Pseudo-spatial Projection
With mental breakdown affecting the target, you get not one, but two doppelgangers to help with the fight. Follow that up with something to avoid damage based on your enemy and you should be able to put them down.
Feel free to post your combos!