Most awkward best man speech I've ever heard was at a wedding in South Dakota. The groom's extended family was Lebonese and very, very conservative. Many of them had flown over for the wedding.
The best man phrased his speech as advice to the bride, like "I've taken care of him to this point, now it's your job, here's how you do it." Which is a novel idea, except he aired allll the dirty laundry like:
Sometimes Alex will eat too many 'shrooms and you'll have to take him to the ER to get his stomach pumped. Sometimes Alex will smoke too much weed and you'll have to get him to put pants on before going out in the snow.
This went on and on, to the point where the groom was pulling on the best man's arm to sit down and shut up.