Off the cuff, I'd say that I've never met a holiday that I didn't like. We even invent our own firstfruits holidays whenever a food that we love comes into season, like the old fashioned strawberry festivals people had! We turn Election Day into a holiday by taking the whole day off, taking the girls out for breakfast where we read editorials on the issues and candidates out loud from the paper. We even started making colonial costumes to wear on Thanksgiving and Election Day (to prod people into voting).
I personally love All Fools' Day and think nothing could be finer than having a topsy turvy day. Nor can I object to Valentine's Day, or even Sweetest Day. Not to sound like a Moulin Rouge (the movie) Bohemian, but beauty, truth and love, romance and chivalry ought to be celebrated wherever and whenever they occur! When my girls are old enough to notice that others have lovers when they do not, I'll still be lavishing them with their own gifts and I'll coach them to play friendly Valentine's Day pranks as I did before I was allowed to date. As I see it, it doesn't matter to me whether other people get materialistic about the holiday, it doesn't change how I celebrate.
That said, the "holidays" I'm least interested in are political "official days" and "appreciation days" and "this or that months." The only Labor Day I'll celebrate are my daughter's birthdays. We all work, we don't need a day of work to mark that we work. Nor am I impressed with modern Mother's Day, Father's Day, Childrens' Day, Grandparents' Day or Parents' Day, all of which I think were superceded by Mothering Sunday, which was a holiday because of the tradition that that day everyone would go to the parish they grew up in, which resulted in family reunions.