Lorne was my favourite character on the show-to me, he was the heart of Angel, the emotional core, and welcome light relief from what was very often a dark show. At least until the final series, when Lorne himself became dark (but I don't like to talk about that). I never met Andy, but I loved him dearly, he was an amazing performer and clearly a lovely man. As for top 5 Lorne moments...oh, dear. Alright, here goes nothing:
5: Lorne's debut. In the opening scene of 'Judgement', we saw a close-up of a green demon, and my first reaction was, 'Okay, who's this villain?' And then he started singing this cool jazzy version of 'I Will Survive'. Instant love. For me, anyway.
4: 'Happy Anniversary'. Lorne and Angel team up to stop a guy from stopping time, and on the way, Lorne has a few insightful words for Angel, who's recently turned dark. 'Man, you just get darker and darker. And the weird thing is...your aura? Beige.' ' Unless, of course, we don't get there on time, in which case, you'll be frozen in this crappy mood forever.' Classic episode.
3: The Pylea arc: The last 4 episodes of Season 2 were Lorne-centric, to my delight, as he returned to his homeland of Pylea. Cue rejection, decapitation, and a gorgeous little rendition of 'Somewhere Over The Rainbow'. My favourite moment from the episodes was Lorne, upon realizing that the book they need to return to LA was left behind, snapping, 'You know, ordinarily I handle bad news really well. I just drown my sorrows in an ice-cold gin and tonic, little squeeze of lime...except for they don't
have them here!' It's all in the delivery.

The decapitation bit scared me though, thinking Lorne was dead.
2: 'Life Of The Party': Another Lorne-centric episode, where Lorne organized a Halloween party at Wolfram and Hart, but began to act very out of character, and in the process, people began to act exactly as Lorne tells them to. It was a very funny episode, but also a bit sad, as it turned out Lorne had had his sleep removed as he was under so much pressure. My favourite moment: the opening scene when Lorne belted out 'Don't Leave Me This Way'. I still love that song.
1: 'Spin The Bottle': Still my favourite Angel episode ever. A spell Lorne did to restore Cordy's memory went awry, causing everyone to revert to teenage versions of themselves (except Lorne himself, sadly). Lorne narrated the episode, and my favourite scene was definitely a moment where Lorne, tied to a chair and apparently unconscious, broke the fourth wall, announcing, 'I know I'm supposed to be unconscious during this part of the story, but can you
believe these mooks?!'
Sorry for the lengthy reply. I still miss him so much. RIP Andy...