I thought that the whole party section was inspired. Such a simple concept but what a great way to see the characters in their interactive element for one last time. The banter, the humour, the character-writing was absolutely oozing in class. From Garrus and Zaeed obsessing over the home defense in Shep's apartment to Joker ripping the p1ss out of Cerberus in front of Miranda and Jacob, to the whole EDI/Tali/Traynor conversation (or the Joker/Traynor convo in the alternate party) - it was all utterly superb.
And that final scene......gulp.