Here are my current favourite "It" bags that I would invest in, if I had the money:
The Marc Jacobs "Stam" bag. The design has been around for ages, and there have been many high street spin-offs, but I love the zig-zag pattern on this version.
The classic Chanel 2.55 has been my ultimate bag for a long time. I have a Mark B copy, but it's not as good as the real thing, and has biro doodles drawn all over it from when I got bored once in a Psychology lesson.
I have big love for this bag. I think it's gorgeous and combines everything I want in a bag - secure, can be worn on the shoulder and be carried on the arm AND I bet it has loads of pockets inside. I fear it will sell out before I gather the funds to get one, but there's always sample sales. I considered getting a Bayswater, but as someone just told me, everyone has one, and I shouldn't sell myself short.
Normally I hit Topshop, H&M or ASOS for my bags, because of price limitations, and they also have good designer copies. Normally, I don't like River Island's bags - I always think they are too gaudy or too patent, or just not quite right, so seeing this bag while in town with my friend, made me realise that sometimes they get it right.
It reminds me of a Chloe bag I saw on a blog (that sadly I can't remember the name of or find the link to). I really like the idea of nude snakeskin (great trend combination) and at £34.99, it is within my price range.
I may have to buy it when I make my trip to London this weekend.