I'm not afraid to say it. This episode scared the **** out of me! Any scene featuring the zombie goa'uld really freaked me out. Especially when Daniel's in the rubber room with SG-1 and one of the zombies appears behind SG-1 and then Daniel laughs hysterically. That combined with the eerie music and sound effects really sent shivers down my spine. The same goes for when Daniel thinks Jack's being possessed by a symbiote and then Janet thinks Sam has.
However, I loved the bit where Jack succumbs to the virus:
"I feel I must apologise in advance for anything I might say or do that may be construed as offensive as I slowly go NUTS!!!