My favorite is NGC 104 (47 Tucanae) at very high power. Otherwise, it's NGC 5139 (Omega Centauri). I'll be seeing both of them again from the Bolivian Andes by the end of the week!
Because it hasn't yet been mentioned in this string, let me put in a good word for M4. It may not seem as brilliant as M13, M5 or M22, but its unique shape, its breadth and interesting possible astrophysical history commend it to us observers in the mid-northern latitudes. Besides, it is prominent in our southern skies these nights, and will be a great target if you find clear, dark skies around the time of the new moon next week.