My favorite things that I use the most are
(1) my Cannondale jacket with removable sleeves. What I like best about it is that the sleeves attach with magnets, and it is SO easy to take them off and put back on compared to zippers. They also come off as one unit and could even be worn as a bolero. The remaining vest has lots of pockets which come in handy. I'm not sure Cannonale still makes it.
(2) my Terry bolero. Perfect for cool mornings and packs away to almost nothing.
(3) Falcon Safety Aquablast air horn for dog deterent
(4) a bento box that attaches to my top tube. Very handy.
Grits
2010 Trek 5.2 Madone WSD, SI Diva Gel Flow
2002 Terry Classic, Terry Liberator