"Spah sappin mah sentry! ...and miners!" image - Eternal Armageddon: The Devastation mod for C&C: Yuri's Revenge

Spies can provide some combat support by using their latch-on EMP Emitters to disable vehicles and base defences for a small period of time. This can be very useful during assaults. Just remember to employ some guard dogs or advance sensor systems if you don't want these buggers messing up your contraptions...