Wow, where to start....Ummmm, the only answer I can come up with is It Depends....
Tank size is obviously going to be huge with that stock you mentioned.....I would suggest a larger pike then the Sax species because of the size of tank mates you mentioned although some Sax Pikes do get to 12 inches like Sveni and Saxatilis themselves.
The Lung Fish, I don't know about, that could go either way I suppose becasue Lungs have a bite from hell, usually aren't that aggressive though so the pike may see them as a threat based on the shape and attack first and fast...>This goes for the gars as well. Eventually they will be large enough to eat the pike, but while young, a Pike may take offense to them based on the body shape and it can quickly kill a young Gar.
Basically, Pikes aggression varies a great deal between species and individuals. Mostly they will fight back if picked on but they do not attack first. The thing with pikes is they do not seem like like fish that are shaped like them because they seem to see them as competition and filling the same niche in the tank. They don't like that. Gars I think would most likely be my concern in that situation.
Anyway, If I were you, (im not so take this with a grain of salt) I would look into getting a much larger pike, Maybe a Ven, Strigata, Lent (possibly but lents are mean) or basically something in the Lugubris complex because on average they are larger and thicker.
So the Fire Eel should be fine as long as it is larger then the pike and based on that
species final size of close to 30 inches, you will need a pike that is going to obtain a rather large size in order for it not to be considered food by the eel although the Pike may end that before the Eel reaches maturity and the size flip flops.
I have no experience with Rays but from what I've read and seen, they should be fine together, size pending. Pikes will not see the ray as food or the competition based on the shape of the Ray. The Ray however, may predate on the pike if the size difference is to great because being a cichlid, pikes 'sleep' at night and are easy targets for a ray to come and pounce on. But if it is to large for the ray, I wouldnt worry about them.
The Ghost knife should be fine but the Pike can easily kill a knife if it decides it no longer likes it, they aren't really aggressive and Pikes usually aren't that bad, but if something gets on their nerves, they will fight back aggressively and they take large bites.
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