Had just purchased a Piper Pacer and was taking it to my home field. One of the last things the previous owner mentioned was 'don't takeoff on the right tank' and placarded on the panel was a similar statement. Piper, in the interest of saving a buck, hadn't plumbed a fuel line on the back of the tank so, when the wing reached a certain angle of attack, all the gas ran to the back and you got the big mag drop. Without a pause, I blythely opened the throttle, popped off and RRRrrrrrrrrr..... - headed towards quiet. Fortunately, my hand instinctively reached for the tank selector switch and order was restored. Needless to say, that tank got another fuel line and became my cruising tank from then on.