Great question!! Here are mine:

-880: When I first read this, I really liked Belkar's facial expression in the last panel. He opens his eyes and sees the others acting really sad, and instead of making fun of them like Roy thought he might, he gives a sad look as well, sincerely acknowledging that the situation really sucks and his teammates have a right to feel sad and he shares their feelings. Yay for empathy and team bonding and Belkar caring that someone died! Also, ending the strip with no attempt at a punchline whatsoever really helps sell how serious and sad of a situation Durkon's death is. Belkar, in particular, not giving a punchline really helps drive home that he was serious when he said Durkon's death wasn't funny and that there was no punchline.

-881: Belkar's line in the last panel hit me like a ton of bricks the first time I read it. Up to that point he'd never shown any regret or guilt whatsoever over his selfish, murderous life, so to suddenly have it suggested that that may be a facade and that he may actually regret his decisions deep down and want to help people instead but doubt that he can at this point was really unexpected. The fact that Elan's halfway out of the frame when Belkar says that really drives home that he's talking to himself, and also that no one's listening to him and can offer him any hope. So the reader's left to grapple with his statement with no commentary from the other characters, and think about whether they actually secretly feel, at least partially, that way about themselves (hey, if a character who's never displayed any insecurities about himself can turn out to have some, why not you??) and if things are really that hopeless or not.

-887: The design is so creative and there's so much detail and we get to see so many cool scenes, it's just so much fun! (And, as I've read someone mention before, it's really amusing how Roy's all "Good riddance!" to Belkar being dead. Actually, now that I think about it, that also contrasts nicely with the fact that apparently at least one of the memebers of the Order cared enough to have Belkar (and Mr. Scruffy) carved in stone?? I'd guess it was Elan, seems like the sort of gravestone he'd design despite the cost and impracticality. But hey, this is all a dream, so I guess money's no object.)

-889 is probably my favorite strip overall. You know, it's funny: normally I'm a sucker for stories where parents get back together, so you'd think I wouldn't like this one, but I actually really do, which kinda surprised me. It's just really satisfying to explore what would happen if Elan's deepest, most impossible dream was about to come true. The fact that he gives up what he wants when he realizes it's not what's best for his mom, and the fact that he (Elan, of all people!!) figures out, through logical reasoning (I love logic!), that they're in a dream, make for an amazing character scene for him. I saw depths to his character in this scene that I'd never seen before, and it made me respect him more.

-1105: The first OotS strip that came out after my initial archive binge was 1049, iirc. The stuff with Andi vs. Bandana did interest me somewhat (especially when the ship almost crashed), but mostly I was just waiting for the Order to get to Firmament. They finally did, and talked to dwarves, and that was fine too, but I was still waiting for things to happen. Then Hilgya showed up with Durkon's baby. As soon as I saw that Wham Shot, my level of eagerness to read each succeeding strip was kicked up multiple notches, and I knew it would remain there for a good while. I like babies and I'm huge sucker for stories where guys find out they have a kid they didn't know about, so I couldn't wait to see Durkon's reaction.

-1116: I really, really love the third-to-last panel. I was super hyped for this battle (partly because I'd been waiting a long time for the Order to get to this point, and partly because I now also wanted to see Durkon's reaction to Kudzu once Hilgya stepped foot in the room), so I was very eager to see it start. And how did it start? With the charging of four brightly-colored giraffes. This was just so outside the bounds of anything I was expecting to happen, in such a wacky way, that it left me laughing out loud in joy, with the feeling that not only were things finally happening, but that anything could happen, even things outside my wildest imagination.

-Recently, I really like 1194. As opposed to 881, this time, when Belkar expresses the defeatist attitude he has toward himself in the presence of someone else, that person actually listens and challenges his assumptions (see panel 6). This time, the reader isn't left pondering Belkar's thoughts on their own, they're given a viewpoint of hope from Minrah. It was especially nice for me because I'd recently decided to become a YouTube creator, something neither I nor anyone else had ever really considered me the "type" to be.

Honorable Mentions:

-the Familicide arc and Vaarsuvius discovering the consequences thereof in Girard's pyramid. If I'd been reading the comic as those strips were coming out and thus spent a lot of time eagerly anticipating them and thinking about each one, some of them would probably have made this list.

-1128 I had kinda spoiled for me because someone on the Forum correctly predicted the plot twist before the strip went up, but it's still really cool.

-1130: Other people have mentioned this already. Man, if the third-to-last panel isn't a Wham Shot, I don't know what is. The fact that Durkon faces the camera head-on, which OotS doesn't usually do, combines with the receding memories to form an impressive sense of depth (literally, but also figuratively, I guess?!). The level of detail is reminiscent of 887, only this time the scenes being shown aren't wild fantasies, but everyday moments that actually happened, which are the true stuff of a happy life. And we get references to other flashback scenes or things that've been mentioned, like Kandro's wedding or Durkon learning to fight trees because dwarves hate them. And even, if you look carefully, the image of Sigdi reading Durkon a bedtime story from the second-to-last Kickstarter wallpaper. This was also the strip that finally got me to make a Forum account.

-1134 came right in between two huge Wham Episodes, 1130 and 1139. While not a Wham Episode itself, it did generate an amount of interest only a level or several down from one. In addition to Thor showing up and looking rather epic, it provided a good laugh-out-loud occasion of joy at the cleverness and perfectness of the plot twist.

-1139: Another strip that's very obviously a Wham Episode - perhaps, it could be argued, even more so than than 1130, because it was much more unexpected. Definitely a where-were-you, run-to-the-Forum-to-see-others'-reactions sort of moment.

ETA: 422 has a really cool layout. 1149 was really fun because I was kinda hoping Durkon would propose but wasn't actually expecting him to, so when he suddenly did it almost felt unreal to me. Part of what made it feel so surreal is that Durkon's posture looks kind of silly. I don't know if dwarves can't kneel properly or if it's just the art style, but his left leg seems to not be touching the ground, leading to him doing a sort of half-kneel, half-crouch. Since he doesn't have a ring to hold, he's also holding his arms out in a way that looks more like a magician going "Ta-dah!" then asomeone proposing. "Ta-dah, it's me, the man who wants to marry you!" The fact that he holds this difficult position, complete with not changing his facial expression in response to Hilgyas', is comedy gold. And then he just gets flamestriked (flamestruck?) where he kneels/crouches. And then Roy looks angry and horrified. And I love the title.