I couldn't help but start with one of the core apps I consider essential (to me anyway!) on my phone, a terminal. The terminal app being developed for ubuntu has some wonderful features built with a touch interface in mind. One of the biggest issues with touch is having a terminal ready keyboard with things like page up and down, arrow keys, and not to mention being able to use keyboard shortcuts like ctrl+d, ctrl+z, ctrl+c, etc. This has been handled rather elegantly with a long tap menu as you can see below, in addition to a panel that optionally appears at the top of the application.
Dmitry Zagnoyko has already landed a few tests for some of the features present, as you can see below. Execellent work Dmitry! A basic testcase exists now for each of the panels and the circle menu.
Help Dmitry and the terminal app team make sure all the features work properly for you upon release. Get involved and add a test. The initial setup work has already been done, and there are existing testcases already written. Grab the terminal branch, add a testcase from the list of needs, follow the tutorial for help if needed, and propose a merge.