xs1100 - rear top case luggage
I already had a luggage rack so why not have a lockable case. I am commuting on the bike all the time and the hard storage is very convenient. I don't care for how the bike looks with the luggage rack or the case, but its too useful to go without.
I got a Shad SH29. In retrospec I should have gone a size up. Out of the 3 helmets I have, only one would fit in the case.
One thing I do really like about the Shad versus other case, it can be opened and closed without they key. If lock it, you need the key obviously. But you can leave it unlocked and still latch and unlatch the lid. This makes it quick to get in into but still secure when you need it to be.