I have a 2011 LHT just purchased in November from Harris Cyclery,(nod to the Great Sheldon Brown).
Assuming you bought a brand new, stock, LHT here is what I did. I am also assuming here that you will be using the bike for touring.
Added peddles as the bike has none. Your choice on type. (This is a topic on it's own)
Added SKS fenders.
Added two bottle cages.
Added air pump.
Added front and rear racks. (This is optional as you may choose to haul a trailer, again....it's own topic.)
Added lighting and sound. (Bell or horn as long as you can be heard)
I also bought a Brooks Flyer saddle which I have yet to install because the stock seat turned out to be pretty comfortable for me.