I was involved in a lunchtime discussion yesterday about the 'essentials' to take when you go cycling.
The answers ranged from 'credit card and a 'phone' to a full workshop kit (the latter wasn't entirely serious - though if you're taking out a group of fairly novice cyclists it's hard to anticipate what mechanical problems they may have)!
The answers also depended partly on whether the trip was short and urban or an exploring the Pentlands or longer journey. in addition it depended on the extent to which rider was keen to do DIY.
The taxi option (they are obliged to carry bikes) can be a useful backup, which is a small commute cost - unless you have frequent mechanical problems...
The conversation moved on to other items - two sets of lights (not just as a spare) and appropriate clothing.
What are your essentials - and thing you 'should' take but seldom do!
New Flickr group - http://www.flickr.com/groups /what_do_you_take_when_you_go_cycling
A lot of the early photos were found in a 'what's in my bag' thread, so show what people actually take on (probably) short, urban commutes where punctures and breakdowns don't seem to be a concern.
Update - some of the posts below demonstrate a slight gender split on what is 'important'.