This card has an obvious synergy with Noise: Hacker Extraordinaire as already mentioned. If anything in a Noise deck it serves as a 2 virus that aligns directly with your current game plan.

Where this card really becomes interesting however is in a cutlery deck (Knifed, Forked, Spooned) and perhaps with Parasite. The high trash rate of corps cards should quickly build up counters allowing you to further deny them of that truly essential ice. In this situation if Eater is used it's possible to install 1 Eater and 3 Harbringer for 3 virus tokens per ice trashed without having to increase your memory at all. All that's left is for you to find enough clicks to use them all!

It is also worth noting that cards such as Hivemind, Incubator and Virus Breeding Ground all provide Noise (specifically) with ways of creating a deadly amount of card milling when combined with Harbringer.