Continuing with the basics that companies persist in getting wrong:
I like predictive text. Having used Siemens, Sony-Ericsson and Samsung phones, that means T9. On each of those phones, I have entered large numbers of words into the dictionary, most of them names, some swear-words, some obscure. Occasionally, due to rushing, I will get it wrong and have to start again. Which leaves an incorrect word in the dictionary. I would like, therefore, the following features:
Being able to edit the dictionary.
Why is this so hard? Surely I should be able to remove words as well as enter them? Granted it's not, given a decent amount of RAM, something that should ever be necessary unless the user makes a mistake. But at that point, the user should have the ability to fix said mistake. Or the sheer satisfaction value of eliminating a name, perhaps.