It depends where you fish. There are some waters with special regulations such as only one fish over 16" or a 2 fish limit. The states I trout fish in (MA VT NH RI) generally don't have size limits for trout, although the daily bag varies from 5 to 12 per day. In most of the places I catch brookies,(small brooks, bogs and beaver ponds) a 10" fish is a nice one.
I roll them in flour seasoned with salt and pepper and fry them in butter. They taste delicious. Other fresh water fish that I really enjoy are smelts (jigged up through the ice), yellow perch, landlocked salmon and, when I can catch them, walleyes. But the brookies are my favorite and when I fish for them I'm looking to catch enough for a feed.