It's hard to come up with one standard of speed. As others here have noted, it depends on the person who starts the tune, it depends somewhat on regional styles, where there are variations on speeds (Clare style slower than Northern styles), depends on whether you want variety of tunes at the sessions, and it depends on whether you're sounding rushed or relaxed at a particular speed. Take these all into account, nd in time you should be able to get a feel for what seems right, and comfortable. As for the top ten, I've noticed a good many Celtic musicians are in the health professions; nurses, lab technicians, some doctors, so in honor of them here is my top ten:

The Wind That Shakes the Barlow's Syndrome Sleep Mastectomy Old Hydrocephalus, You Have Killed Me The Liver Scan Hornpipe Harvest Homeostasis Walter Sammon's Granulocytosis The Barium Swallowtail Jig Flagellums of Dublin Boil the Bronchus Early Mucosa In The Glen