Minuum - The Little Keyboard for Big Fingers is a good option if you have a hard time hitting the correct letters on a standard keyboard. It offers two different modes for typing and incorporates swipe controls to minimize the number of buttons that appear on the screen.
Teaching autocorrect: While most keyboard apps gradually adapt to your typing preferences over time, this one actually allows you to teach the autocorrect as you go. You can choose what you've actually typed if that's what you really wanted to say, and you can press and hold certain suggestions to instruct the app to unlearn them and not show them again in the future.
Minimalist interface: The main keyboard in this program shows only letters, so that it takes up the same amount of space as a standard keyboard but still provides more room for you to hit each letter accurately. Swiping gestures make up for the lack of specialty keys, and they include swiping right for a space and left to delete.
Continuous readjustment: The autocorrect in this keyboard doesn't just focus on individual words. Instead, it will continuously readjust as you type, gathering context from the rest of your sentence and making corrections as you go.
Minimized mode challenges: In addition to the standard keyboard in this app, there is also a Mini Mode that features just a string of letters that you have no hope of hitting accurately, but that you don't have to -- in theory, anyway. If you want to use this feature, it's definitely better to spend some time teaching the autocorrect through the main keyboard first; and even then, it's a tough adjustment to make when you do try and switch to the Mini option.
Minuum is a good option if you have a hard time typing on a regular keyboard for any reason. Its enhanced autocorrect options are a nice addition, as is the added space for letters and the elimination of extra keys. Mini Mode may not be for everyone, but it's still a nice option to have as well. The app costs $3.99.
Just swipe up and down to switch between full and mini modes: