Horatio is the scholar;
Marcellus, the soldier.
Hamlet has called them both friends.
We never see Marcellus again after this scene;
Horatio hangs around.
Two more friends turn up in a scene or two. It strikes me that this is one of the few plays that features multiple friendships. Women tend to have a single friend. Rosalind has Celia; Helena has Hermia. And men tend to be rivals or colleagues. Lysander and Demetrius, the Mechanicals. Oh, wait, what about Hal and Falstaff – and all the guys at East Cheap. There we have a group of friends and also a Prince. The connections between Hal and Hamlet are several. For one thing, we see the friendships fall away as the Princes head to their inevitable end, one to kinghood, the other to tragedy.