"And Then There Was Silence," both the studio version and live. Just to elaborate: we're talking about the longest song coming from a band known for Epic Rocking. It alone took up half the recording time that went into A Night at the Opera, and Hansi himself considers it to be the greatest song he's ever written.
The first live album, Tokyo Tales. Hansi gets the crowd to wholeheartly sing the intro for Journey Through the Dark on first try and they've only just begun. When you get this kind of audience participation, especially with addressing them in an unfamiliar language (most of the crowd probably found his English hard to understand...) you know you're a freaking god on the stage. Bands that have been in the business for years can't wrap a familiar audience around their fingers like that.