1 & 1/3 fluid ounces or 4 centilitres of Tequila
2/3 a fluid ounce or 2 centilitres of Triple Sec
2/3 a fluid ounce or 2 centilitres of Rose's Lime Juice
Splash of Grand Marnier
Dash of Blue Curacao

This is the one!! (Or as close to it as most of us will really get) Sammy Hagar invented it, I just want to share. Over fresh ice, pour all ingredients except blue curaco. Shake or stir well. Strain into a martini glass (with a kiss of salt on the rim). Add blue curaco gently and it will layer to the bottom of the glass. Garnish with lime.