I have ALOT of bags but only find myself using about 3 of them. My most used (and most loved) is this leather one from River Island....
I've had this for about 4 years now, my friend bought it for me from a charity shop called New Life. Its a huge shop that gets clothes and accessories donated from stores such as New Look, River Island, Debenhams, etc.. Everything is priced from a couple of quid, there are some right bargains to be had. This bag for example, i think my friend paid about £8 for it and it was selling in River Island for well over £50.
This bag has been through the wars, its carried everything from baby bottles to my sweaty gym towel and has been everywhere with me, it is still as good as new. I love the fact you can wear it over your shoulder with the smaller strap or use the long chain strap as an across the body bag.
It has a zip compartment and a place for my phone inside and two zip pockets on the front.