When dealing with goblins, if it isn’t nailed down, it’s headed your way.
The Combo
With Conspicuous Snoop in play (as early as turn 2), Boggart Harbinger tutors Kiki-Jiki, Mirror Breaker to the top of your library. Snoop now has Kiki-Jiki's ability to copy itself, which creates an untapped copy of Snoop also with Kiki-Jiki's ability. Rinse and repeat for enough to be lethal, then tap the last one to copy the Harbinger and put Sling-Gang Lieutenant on top. All Snoop copies now have Sling-Gang's sacrifice ability, sac them all to drain the opponent out.
Goblin Matron and Goblin Ringleader find combo pieces.
Goblins
Aether Vial for cheating Goblins into play.
Skirk Prospector for turning Goblins into mana.
Mogg Fanatic for an alternative to Sling-Gang that allows Snoop copies to sac themselves, also kills Ragavans dead.
Mogg War Marshal makes tokens on entering/dying (with Skirk Prospector, this becomes a Pyretic Ritual).
Munitions Expert for removal.
Goblin Chieftain to give Goblins haste and a lord effect to make 1/1's better.
Pashalik Mons as an alternate win condition of sorts in grindy games (with Sling-Gang out, it can hit for 2 per Goblin sacrificed).
Den of the Bugbear for a Goblin manland that makes tokens.
Sideboard
Goblin Cratermaker for killing Plague Engineer mostly, but also artifact removal.
Goblin Trashmaster for artifact removal, as well as another sacrifice outlet AND a lord effect.
Magus of the Moon for nonbasic land hate.
Alpine Moon for land hate.
Thoughtseize for hand disruption and protecting the combo.
Leyline of the Void for graveyard hate.
Void Mirror for Tron/Artifact hate.
Maybeboard
Krenko, Mob Boss as another alternate win condition of sorts, for swarming the board with tokens (also nutty with multiple Snoops on board and Krenko on top of the library).
Goblin Warchief to give Goblins haste and make them cost less.
Goblin Chainwhirler for a token/mana dork wrath.
Fury mostly for a free board wipe.
Obsidian Charmaw for nonbasic land hate.
Tarfire for a tutorable removal spell with Matron/hit off Ringleader.
Warren Weirding for a tutorable edict effect (that can also be used on our own Mogg War Marshal for value).
Boil for Island hate.
Blood Moon for other nonbasic land hate.
Plague Engineer for the mirror, other tribal/aggro decks.
Knucklebone Witch as a one-of for a big beater with sacrifice effects.
Relic of Progenitus for graveyard removal.
Damping Sphere for Storm/Tron/Prowess hate.