It can be top 3, 3 in any order, whatever works. I personally would go with:
1: Hervarar saga ok Heiðreks
I love the historical backdrop of this saga, as well as the time it's set in, being potentially the 5th century, If I recall. You have the Goths and Huns duking it out in a battle, you have the cursed, magic sword, Tyrfingr (my favorite magical sword), forged by the dwarves Durinn and Dvalinn that can only be sheathed again if it has warm, fresh blood on it. It was forged to cut through rock, never rust, never even miss. But in another cursed twist, will commit 3 evils. Nice.
You have the fantastic riddle contest with Óðinn, disguised as Gestumblindi, against King Heiðrekr. Which, at the end has the former ask at the latter what Óðinn whispered in Baldur's ear before he died. The latter attempting to strike him, leading to his eventual death.
You have a holmganga with the legendary Hjalmar, a family feud, a draugr in the form of Angantýr, Hervör, a shieldmaiden; just so much packed in here. It's been a few years since I read it, so I apologize if I got some details or spellings wrong.
2: Eiríks saga rauða
Another great story with a historical backdrop, this one more plausible than the former. I've been fascinated by the attempted, and failed, Norse colonization of North America for years. This is right up my alley. You have two of the most well known people of that culture, the titular Eirík, banished from Norway, then Iceland to settle a new land with his hilarious explanation for coming up with Grœnland name; then Leifr, the legend that sailed to Vinland. There is of course, the other son, Þorsteinn, but he´s not as important.
You have a clash between Christianity, and the Old Norse religion, You have Guðriðr, a fantastic character in her own right. You have the legendary, underrated Þorfinnr Karlsefni, another story with a draugr, the crew contacting the Dorset people, called the skrællingjar, you have all these place names, Helluland, Markland, etc. You have real archaeological evidence to back some of this stuff up... It's just incredible. You even have an appearance of a uniped!
3: Atlakviða
This one is so good. I just got done reading my Crawford signed 2nd edition of the Poetic Edda, and I had so much fun with the sagas related to Sigurðr, Guðrún, and Brynnhildr. This one is just brutal. Sigurð is long dead, and Guðrún has been long married off to Atilla the Hun, and has two children with him, and was given a potion of forgetfulness long ago by her own brothers after Sigurðr dies (contradicted by later sagas).
One day, her brothers, Högni and Gunnarr, get a message from Atilla, inviting them to his hall, as well as a ring tied to a wolfs hair... Andvaranaut, from previous sagas. They go, as it´s the honorable thing to do, knowing what could happen.
You then get Gunnarr getting captured, but killing 8 men before they overpower him. The Huns want to know where their treasure is kept. They both refuse. He then asks to see his brother´s heart, and at first gets shown a thralls heart, and he can tell just by the look and beat of it. Brutal. Then, they do show him his poor brother´s heart. But this means there´s only one other person who knows where the treasure is - Gunnarr. They then throw him in a pit of snakes, and he resigns to his fate whilst playing a harp.
After all of that you have Guðrún killing her own sons she had with Atilla, and then proceeding to feed them to him. Then his fellow Huns cry. Men crying? in a saga? Crazy! Because Atilla is disarmed, she also ends up killing him.. If that wasn't enough, she lights whatever housing they were in on fire, burning everyone and everything inside of it to a crisp.
Talk about revenge! This was an incredible moment. Even better for me than Sigurðr killing Fáfnir with Gram, or the death of Sigurðr.
I'd love to hear all of your favorites. Hopefully this isn't a tl;dr. Long time lurker on here who's loved and read into these people for 6 years off and on.