- Cooking & laundry timers
- Reminders (remind me to do X when I get home)
- Directions (Take me to the nearest X, take me home, etc)
- Checking hours of business (what time does X close today)
- Initiating phone calls (Call X)
- Checking weather (is it going to snow today? How cold is it right now?)
- Conversions (what's X ounces to ml)
- Quick stock checks (what's X stock price)
- Playing music around the house (play X on the kitchen speakers)
Additionally, I've found myself using Android's voice recording capabilities to dictate text all the time. It's just so much faster than typing or swiping.
I haven't an iPhone for a few years, so I can't compare with what Siri is capable of today.