Exchanges, for one, in virtually any industry. Recall that one of the primary concerns after 9/11 were the NYSE, Nasdaq, Mercantile Exchange, etc. Banking centers. Oil refineries. Port. Etc.
If the NYSE building were bombed on an operating day, it would absolutely have dramatic financial repercussions, and that market would absolutely be crippled. Would some simile reappear? Of course it would, just as government would reappear if a full capital building were attacked. But the impact would be major and it would be felt.