One of my friend got me a lovely picture frame that said Gorgeous on it & put a funny pic of me inside! I loved it. She also got me a cool top with a horse on it (no, really, it WAS cool!) & I love horses so I loved that too. Fave bottle of alcohol (Baileys?, Prosecco?) Thorntons chocs? (you'd need to be mad not to love them.)
Another idea that I did for a friend of mine and she loved, is a photobook with pictures from as far back as you've been friends. Photobox or Snapfish are good sites to check out to have them made. Or a great photo (of the two of you or something) on a phone cover from a site like Wrappz. I'm a big fan of personalised things!