1. According to U2Gigs the warhorses are (without including snippets of said songs and with over 500 performances):

    Pride (In the Name of Love) (1056 times played)
    I Will Follow (1053 times played)
    Where the Streets Have No Name (976 times played)
    Sunday Bloody Sunday (976 times played)
    With or Without You (912 times played)
    One (858 times played)
    New Year's Day (804 times played)
    Bullet the Blue Sky (792 times played)
    I Still Haven't Found What I'm Looking For (696 times played)
    Beautiful Day (674 times played)
    Until the End of the World (647 times played)
    Mysterious Ways (638 times played)
    Vertigo (588 times played)
    Bad (563 times played)
    Elevation (559 times played)

    I'm quite happy for the band to keep on playing (from this list) :

    Streets - you cannot have the intro that is Streets missing from a show
    WOWY - even though this has become anathema for some, I like to hold onto my partner and sway together during this song
    One - (ditto)
    BTBS - The only 'ropey' version was the Vertigo tour for me, otherwise play it boys play it
    ISHFWILF - another one that now grates on people but it's such a perfect song
    Beautiful Day - not everyone's favourite but much much better live in concert - and an awesome coda
    UTEOTW - Need to have some proper guitar songs in there and this one goes to another level
    Bad - Never heard a poor live version so keep it coming

    The rest you can drop anytime for 'rarer' songs