The Scout & Infiltrate special rules both confer Outflank to units that have either of those special rules.
So the list of possible Outflanking units looks like:
- Stealth suits
- Pathfinders (with Devilfish if taken as a dedicated transport)
If you're running FSE you can also use the Warscaper Drone to give Outflank (and acute senses) to any Commander or member of a crisis team with a drone. So if your happy to attach your Commander to a unit the Outflanking list gains:
- Crisis team
- Firewarriors (attach Darkstrider or a Warscaper Commander)
- Breachers (attach Darkstrider or a Warscaper Commander)
- Sniper team
Take several Outflanking units and combine with Positional Relays and you can completely encircle the table. Having a unit of Crisis suits or Broadsides waltz on from your opponents own table edge at the start of turn 2 is pretty funny...