Sports stopwatch with:
• giant digits and adjustable theme (color, font, size, spacing, format)
• control with both on-screen buttons and volume buttons
• lap-timer
• delayed-start (with audio 3...2...1... countdown)
• screen lock mode to prevent accidental count stoppage due to splashes (you are of course responsible for ensuring your device is waterproof)

Free, small, no ads, open source (github.com/arpruss/simplestopwatch).

As a bonus, includes a giant number clock (swipe up/down to switch between clock and stopwatch).

I made this so I could easily see the time while rock climbing at the gym 50 feet up. It's also useful poolside for swimming, and for other sports where you need to see the time from a distance (or close up, if you want).