Unlimited augmentation upgrades
Make sure you have no room in your inventory, then talk to Jaime Reyes at Tong''s lab, the time he gives you the upgrade.
You will then tell him that you have no room, he will drop the aug upgrade on the ground but he will still have it next time you talk to him.
This is also possible with medkits from the terrorist prisoner in level 4 UNATCO HQ when you break out of prison.