Those games which still hurt after all those years
Ireland:
Of course there are lots of painful last minute goals and loss of play offs (Belgium in particular) but the 1-1 draw with England at Wembley in 1991 still comes in to my mind the most. The team went unbeaten through the group stages but we had a great chance to beat England on their own turf and for that team to etch their place in history and also more than likely qualify. I can still see Ray Houghton bearing down on goal late in the game with a chance to make it 1-2 and the rest is history.
Shamrock Rovers
I had the pleasure as a kid seeing the great Rovers teams who won the cup 6 times in a row (well the last few anyway including the memorable win over Waterford) but league titles, I hadn't seen thanks to Waterford and others and then came the play off against Cork Hibs in 1971. Rovers were stuffed and I had to wait until the 1980s before the title came Rovers way. I can still remember coming out of the ground as a pimply teenager thinking that was not supposed to happen to the mighty Hoops.
Sheffield Wednesday
Three Cup Final defeats but it is a semi-final loss to Brighton in 1983 I remember with the greatest sadness. Following relegation in 1971, Wednesday had been in the wilderness and were almost relegated to the 4th division until Jack Charlton turned their fortunes around and led them back to the 2nd Division and a cup semi-final against struggling Brighton. It wasn't to be and a poor performance and 2-1 defeat was followed a few years later by another semi-final loss to Everton but they had been promoted by then under Wilkinson.
Other sports
Lots of disappointments in rugby and numerous other sports but I remember most the great Eamonn Coghlan: surely he would win the Olympics in the 1500 meters in 1976? Eamonn had always relied on his sprint finish but for some bizarre reason he took the lead at the bell I think and was chased down and overtaken on the finishing straight. Was it panic? I will never understand it. He didn't even get a medal. He also missed out on a medal in the 5000 metres in 1980 but it is the 1976 Final that I still think about. He must have been devastated. I certainly was.
Sport, the occasional moments of ecstasy also carry hours and hours of pain but who would miss it for the world?