The obvious uses are:
- Archangel on the outside of a server, to force the corp to break or beat the trace, otherwise you bounce their breaker for the inside ICE. It's quite taxing to break, except with D4v1d. The trace is quite strong, so everyone who isn't running a Security Nexus build will probably pay 4-6. And for only 4 to rez!
- Bounce other cards the runner needs during or just after a run. Self-modifying Code, Plascrete Carapace or Clone Chip perhaps.
- Messing up runner cards with counters (virus/power/credits) like Kati Jones or Medium. That taxes the runner a mixture of and .
- Bouncing expensive cards. Good targets include Femme Fatale, Professional Contacts, Yog.0 and Magnum Opus. Most runners don't play too many expensive though. Security Nexus would be a juicy target, but, well...
The trick I've missed so far is to just hold an Archangel in hand. If you can afford to trigger it multiple times, it can be a major annoyance for the runner. This is especially useful if HQ isn't very secure, inviting friendly runners for multiple visits. As an Ambush it is very difficult to trash. Typically an Imp or similar would be required. Using Archangel like this is relatively costly, but can generate a differential.
I can't believe how cheap Archangel is to rez.