If you need "Business Formal" for your work, but are of the thrifty sort who does not like to spend $2-3000 on a suit, the Brooks Brothers winter sale only has a few more days to go.
I make sure I always have a bit of this stuff on hand, if only for weddings, funerals, and special parties. However, my 20 year-old Brooks tux probably gets more use than my suits: I am not in a Business Formal line of work and I have been fortunate lately in not having many funerals to attend.