One of my favorites to get is the "Ramora" Spinal Implant. It fits in the offensive slots in the facility but gives you a defense bonus on Snipers. Combined with 2 Echnida SA-01 (+4% def Snipers) you get a total of +24% defense for your snipers. Granted SCARS are not everyone's favorite type of troops. BUT, even SCAR units have their place in this game. They are super cheap to buy in large quantities at once for defensive infestation runs, for example.
Used in conjunction with the Cardiovascular Implants (-10% cost for Heavy Gunners) x 2, I can buy ALOT of heavy gunners and have a quick boosting effect on the infestation. They are good to use as fodder in those infestation hits and you really do not mind losing them since they cost you so much per hour.