Adhesive tape is a vital addition to your motorcycle toolkit. Whether it's for a personal touch of colour or the temporary reattachment of a broken mirror, or to keep a side case shut, a roll of tape always comes in handy. You can even use it to patch up boots and gloves, when in a pinch.
If you are going to work with electrical cables, then use special insulating tape.
Tape - and especially the really sticky kind - is of course not limited to the motorcycle. Whether you're using it to fasten your boxing gloves or shin guards, or to do the odd job, a roll of tape can go a long way.