"Careful with that axe, Eugene!" is a track by Pink Floyd from their early, Syd Barrett era. The track is a long instrumental, with the title as a single lyric at the music's climax, followed by a prolongued, ecstatic scream.
The track first appeared on the double album "Ummagumma", and a repackaged studio version on the compilation "Relics". A modified version was used in the sound track "Zabriskie Point", entitled "Come in Number 51, your time is up", which has background whispers in addition to the lyric.
People might be inclined to imagine that the axe refers to a guitar, but the scream slightly gives this away. The band did repeat this formula with the track "One of these days", which appeared on the album "Meddle". The lyric in this case was the line "One of these days, I'm going to cut you into little pieces". Some critics cite these two tracks as evidence of Pink Floyd's obsession with serial killers, but there's precious little in the rest of the band's repertoire that supports this. It's probably more like evidence of the chemistry happening in the band members' brains at the time, Syd Barrett's especially.