I won at least 10 games of FFA earlier trying to gold my PDW, I would find a room or something, set it up with a guardian at one entrance, eventually a sentry gun from a vantage point, then eventually another guardian, it was fun and not a single one of them got hacked/EMP'd.
EMP grenades are amazing. I got a UAV from tossing one of them. Destroyed shock charges, guardian, sentry gun, betties, and got an assist a few seconds later.
This. I love it when someone sets up a complicated trap with their shocks and claymores and boom - it all comes down with a single EMP. The AoE plus ability to stop KSRs being called makes them very very useful.