Grixis - Thopters (Standard)

There are a couple different synergies and one infinite combo in this deck. Well actually there is more than one combo, but all of them center around Whirler Virtuosa and creating 3+ energy every time it creates a Thopter. So without further ado here are all the synergies I know of. The fastest I have ever had the combo go off was on turn 4 and can quite reliably get it on the field by turn 6.

Combo:

Whirler Virtuosa require three energy to create a Thopter, there are two different ways to create that energy: Decoction Module & Gonti's Aether Heart. Both Decoction Module and Gonti's Aether Heart create free energy when an artifact enters the battlefield. Panharmonicon can also be used if a Decoction Module or Aether Heart is already on the field to cause said artifact to activate twice rather than once. To get the combo running you need a Whirler Virtuosa, 3 energy and some combination of the following on the battlefield:

3x Decoction Module
1x Gonti's Aether Heart & 1x Decoction Module
2x Panharmonicon & 1x Decoction Module
1x Panharmonicon & 1x Gonti's Aether Heart
1x Panharmonicon & 2x Decoction Module

Synergies:
Animation Module + Decoction Module + Fabrication Module

The way this one works is that when one of the above Module's gets activated it causes a trigger that activates the next module and then the next module. This synergy cost 1 mana for each go around, but gives you 1 Servo, 1 energy and 1 +1/+1 counter.

Animation Module + Syndicate Trafficker

2 mana and an artifact cost synergy. Pay 1 mana to activate Trafficker's ability which gives it a +1/+1 counter. Said counter then cause animation module to activate, so pay 1 mana to make a servo. And then use Traffickers ability again and again till you run out of mana. Best to do this one either after an opponent declares blockers or at the end of their turn, since neither of these abilities are tap abilities.

Contraband Kingpin + Any Artifact

Simple enough, each artifact lets Kingpin scry 1. When you add a Panharmonicon to the mix you get to scry 1 twice.

Glint-Sleeve Siphoner + Fabrication Module

Whenever Glint-Sleeve Siphoner attacks it creates an energy which triggers Fabrication Module and allows you to pump the Siphoner. Over time this can result in the Siphoner become quite large and has won games by itself.

Sideboard:

Metallic Rebuke for dealing with combo decks

Reckless Fireweaver and Marionette Master for dealing with decks that for whatever reason you cannot attack or deal damage to through combat

Battle at the Bridge is removal for dealing with those pesky indestructible creatures that pop up every now and again.