[Agent Wave]

When you dominate a player, they see the nemesis icon above your head. I think there should be a plugin that allows the server to designate a custom particle to be displayed above the dominatee's head that can be seen by the dominater (sort of a "reverse" nemesis icon).

I'm trying to figure out where to start. I've got some programming background but not much experience with sourcemod plugin coding. Anyone have any advice or direction to offer?

[SuperShadow]

You might be able to use this plugin as a basis for yours: http://forums.alliedmods.net/showthread.php?p=906713

[Agent Wave]

Hm, it looks like ModelFun has a particle hat function that might be closer: http://forums.alliedmods.net/showthread.php?p=775016 It can attach the particle to their head and it will follow the player.

Is there an event that's fired when a domination/revenge occurs? I suppose I could check each time a player spawns to see if they're dominated but it seems a lot cleaner to set a bit when the domination/revenge occurs.

On player spawn, I would check that bit and attach the particle to the player's head... but is there a way to make a particle only visible to the person who is dominating them? This works for the built-in nemesis icon. How would I do this with an arbitrary particle?