From what I've seen at Big 4 its mainly helping out with audits of Insurance companies and stuff, helping accountants work out provision for claims and stuff
There are some independent evaluation jobs that Big 4 actuaries do too, one big one that comes to mind is the James Hardie Asbestos claim one which was done by Deloitte (Trowbridge consult.) first and then KPMG Actuaries
Thats all I know
The Accounting firms are pretty big hirers of actuaries though. I think an insurance company would be lucky to have more than a handful of actuaries, whereas big 4 have like dozens