I'm the Field General/Sniper for our group (mostly AoR based); if you know X-Men comics, think Cyclops. But gun based, rather than a mutation. Duh, it's Star Wars!

I'm not a fan of blasters, for a few reasons, so I use slug-throwers. I love my used Czerka Arms Model 38 (5 shot clip):

Damage - 8 Critical - 2 (Jury-Rigged via teammate) Range - Extreme* HP Remaining - 1 Mods - Telescopic Optical Sight*, Slug Supressor & Weapon Sling Special - Accurate 2, Pierce 3 & Slow- Firing 1

My question is, what attachment, even if home-brewed, would be a good combo here, for that last HP? I don't want anything game-breaking (superior could be nasty); just fun, thematic & solid. Thoughts? Ideas?

I've always liked the custom grip from Special Modifications. The laser sight from Dangerous Covenants fits the sniper theme, so that might be a better choice.

With a slugthrower with 1 HP, there's really not much potential to become game-breaking. Superior Weapon Customization would be fine, the things Darth Ferrum suggests are good options as well, and otherwise you could go for the Multi-Optic Sight (night vision, removes obstructions etc.) or the Sonic Scope (shooting people through walls is nice).

Sonic scope.

Nearly impossible to find at rarity 8, and not cheap, but it allows you to shoot through walls (with gm approval) and it's upgrades are all useful for a sniper.

I've got Tracker Goggles already, so leaning toward Sonic Scope, or a Secondary Ion Blaster attachment, if someone can tinker a 2nd HP.