Gymboss (3 ★)
The highly customizable multiple timers are the main selling point of this app, and is the reason why I’m keeping it on my iPhone, despite its major flaws. As others have mentioned, the timer pauses when the iPhone screen locks; also, the individual elements within a timer aren’t editable (to change duration or alert sound). The sounds available are also very limited, and aren’t able to be previewed while setting up a timer.
With a few adjustments, this could be an excellent app. As it stands, with its flaws, it’s pretty good for free.