Some UFO evidence makes me laugh.
Some of it, yes. There's so many hoaxes out there that it's difficult to sort out the fake from the real. However, there have been a few cases that I think have merit. One of the best known UFO sitings happened in Nova Scotia, Canada in 1967 and is simply known as the Shag Harbour Incident. Very interesting read for those not familiar with this particular case http://en.wikipedia.org/wiki/Shag_Harbour_incident.
Another excellent example is the incident that occurred in December 1980 in Rendlesham Forest, Suffolk, England. Personnel at RAF Bentwaters (a base leased to the USAF) reported strange lights in the forest. Thinking an aircraft had crashed, they went to investigate. They said they found a UFO. They took photographs (which they were later told hadn't come out) of the craft and one of the men got close enough to touch the object, which then took off and flew away. The stunned men briefed their bosses, including the deputy base commander, Lieutenant Colonel Charles Halt. Halt got the men to make official statements, including sketches of the craft. The following night Halt was at a social function when a flustered airman came running up to him telling him that the object had returned.
Lt. Col. Halt and a small team went to investigate. His intention, he later reported, was to 'debunk this nonsense'. As they went into the forest, their radios began to malfunction and powerful mobile searchlights cut out. Suddenly, Halt and his team saw the UFO and attempted to get closer. At one point it was directly overhead, shining a bright beam of light down on them. After these events, Halt ordered an examination of the area where the UFO had been seen on the first night. Three indentations were found in the ground where the craft had landed. A Geiger counter was used and radiation readings were taken, which peaked in the three holes. Halt reported it to the MoD and an investigation began.
This was inconclusive, but Defence Intelligence Staff assessed the radiation readings taken at the landing site were 'significantly higher than the average background'. The MoD's case file on the incident has only recently been released under the Freedom of Information Act: http://www.ufoevidence.org/documents/doc660.htm
Skeptics claim that it was the light from a nearby lighthouse that they saw. This is by far, one of the stupidest things I've ever heard. If trained military men can't tell the difference between a lighthouse an an object that they were close enough to touch, then we're all in trouble.
Of course the best known case is Roswell. While the story has most likely been embellished over the years, I find the story of Jesse Marcel quite interesting and pretty credible.
There have been several sightings over the years, by credible people who cannot be easily dismissed. Unfortunately, due to all the nutbars who will do anything for attention, UFO sightings have become something of a joke. It'll probably remain that way until the world gets a look at some physical evidence.