Invoke-SwisVerb takes four parameters:
1. The SWIS connection object.
2. The name of the entity type.
3. The name of the verb.
4. The list of parameters for the verb itself.
You need to take those parameters and put them in a powershell list. This is done by wrapping them in @( ... ). So the full command line should look like this:
Invoke-SwisVerb $swis Orion.APM.Application Unmanage @('AA:516', '2014-02-11T20:00:00Z', '2014-02-11T21:00:00Z', $false)
