Did this with just the knife, nothing else. A weapon (or co-op partner to get to wave 9 faster and/or distract the Juggernaut) could make it quicker, but I worried about accidentally killing him with the gun so I just used the knife the whole time. On the first Survival map there's an archway in that courtyard, on the other side of it in the street there's something that looks like a giant magazine rack. You can simply play ring-around-the-rosie with the Juggernaut using that as your cover. Run around it, stab him, retreat, then just repeat. The magazine rack is so large that he really can't hit you, and you can have that between the two of you anytime you need to recharge your health. The Juggs in this game are nowhere near as trigger-happy as they were in the last MW game. So even if he shoots you, you can hurry back behind the rack. Only real threat he has is that he'll try to melee you too sometimes instead of shooting you. But it's easy to just play it safe and if he goes into that animation, leap back to get behind cover and just attempt to stab him again. Honestly though, he whacked me quite a bit and it never hurt that much. There's faster and more efficient ways, but this is pretty much a guarantee.