This is what I want to listen to in order of importance:

UHF military aircraft (270ish range)
Civilian aircraft (108-136)
Trains
Marine
AM/FM radio (the kind that plays music that you listen in your car)
ham radio
police, ambulance, and all the other stuff

The first 4 are a must, the rest aren't really that important, but I
wouldn't mind hearing them. I'm thinking one of those "full spectrum"
units would be great. I don't know what "trunking" is, but I don't
think I need it.

It also has to have the different "modes" so I can hear the military
aircraft correctly. I heard some scanners can pickup signals in the
military air band, but lack the proper mode to decode the signal so it
can be understandable. My budget is about $300 USD.