C&C was my first 'real' pc game. Got that while still rocking Windows 3.1. The soundtrack was the shit.
Still remember a bunch of the GDI missions, especially that one when you only get the Commando. As a 10 year old, I was in awe of how powerful that unit was. I also remember that fucking Corinth, Greece mission where you land with basically nothing and get steamrolled in a matter of minutes. That mission pissed me off as a kid.
Then there was the GDI guard tower glitch where if you sold a regular guard tower and clicked 's' while it was deconstructing, it would pop back up but leave the infantry that left when it was originally sold.