Here's some from my list:
A PFD for each person, REQUIRED
a whistle on each PFD, REQUIRED
paddle leash,
a VHF Marine radio,
water to drink,
a hand sump pump,
a bow line,
a throw-rope,
a knife,
spare parts (rudder pins, aka shear bolts, some extra spectra line, wire-ties, etc.),
SS tools to tighten everything and install all spare parts,
If going solo off shore, or in rough conditions, a surfboard leash for each person.
If you are going way off shore, an EPIRB.
Here's a couple of old post of my AI toolkit contents:
http://www.hobiecat.com/community/viewtopic.php?t=10418&highlight= (I really should update for the TI)
http://www.hobiecat.com/community/viewtopic.php?t=8424&highlight=
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Hobie Island Sailing since 2006