I'd love to see more skills, skill-lines or systems that encourage direct interaction between players, but are also completely voluntary (so that one player couldn't force an action on another). These would be skills that players could only use on other players, not that they could use on themselves. Things like:
Fortune-Telling: One Glitch tells another Giltch's future (both voluntarily). The Fortune either grants a random (or is it?) buff to the player having their Fortune told (like telling them their immediate future will be "Jellightful", and they receive a buff to Jellisac Scooping for ten minutes); or it fails, and a bad Fortune debuffs the player, instead. I think it would be cool if the Fortune was influenced by the world around the Glitches - like time of day, or what Giant's Shrine is on the Street where the Fortune is being told.
Teaching: Temporarily increases the rate at which skills are learned. Low levels of the skill are weak (don't last long per activation, or only give a 1% increase to learning speed, or whatever), and only allow one Student per Teacher. Higher levels allow multiple Students per Teacher and/or are more effective/last longer. Teachers should obviously have to know the skill they are teaching, preferably at a high skill-level. Teachers can only teach one skill at a time. Students only receive the buff while the Teacher is actively Teaching; the point is to keep players together and social.
Quest-Giving: I know this one has been posted before, but I think it deserves repeating.