Aces is a utility program which lowers the armor of TAGged guards by 1 for one turn. It costs 2 PWR to use, and has a cooldown of 3 turns. Aces can be bought from some Server Terminals for 600 credits.
Aces is found in the Contingency Plan DLC.
Overall, Aces is not a bad program, but it is highly situational — it can work well as part of a specific strategy, but in most loadouts there are better options. At 600 credits, Aces is also quite expensive for a utility program.
Aces lowers the armor level of guards, so it has a similar purpose to the armor-piercing bonuses of Penetration Scanner, Piercing Scanner or a Ventricular Lance. The upside is that Aces works for every agent instead of just one; the downside is that it only works on TAGged guards, so Aces is only useful in combination with Wisp or a TAG pistol. However, TAGging guards makes it easier to avoid them, so being able to attack them is less important.
Unlike armor-piercing bonuses which only affect attacks made by agents, Aces also lets you use Turrets or hacked Obake Drones to shoot guards with 1 armor; hacked Akuma Drones can also be used to shoot guards up to armor level 3, such as OMNI Soldiers.
Because Aces technically works by triggering an algorithm, Central's Antiviral Proxy augment generates +5 PWR when Aces is used, for a net +3 PWR. Aces can therefore be used as a generator when Central is on your team, for an average of +1 PWR per turn if you use Aces every 3 turns.