With bikes using more and more of Allen keys instead of normal nuts, a set in your toolkit is a valuable addition. You get some nifty cycling toolkits today which include a selection of Allen Key sizes, plus some hex sockets and stuff, but I find adding a full key set to your stock toolkit is shockingly cheap and simple. So we did. It proved handy when we had to remove the mirrors at the racetrack and then to put them back. Thankfully, we never needed them otherwise, but it's a valuable addition to your toolkit that requires neither a lot of space, nor a big expense.
Various online stores, Rs 800 onwards