Jacques said

what are the EXACT scales that people expect to hear from a violin? Feel free to list the actually notes if you'd like including the harmonic tones. (I do think that exists, right?)  

Not sure what you mean by the harmonic tones, but the bigger problem is that there is no one set of scales for what people expect to hear from a violin. Classical probably covers the widest - there are pieces written in just about every key there is. Certain genres, such as country, bluegrass, Irish, etc, may have particular keys that are more common in them than most, but even where that's true, it's only going to be true for that genre. It doesn't apply to "the violin".

Like I said, the three most common keys in music written specifically for the violin are D, A, and G, probably in that order. 

D is F# and C#,

A is F#, C#, and G#,

and G is just F#.

The modes Bill spoke of are an idea the Greeks came up with (which is why the names for all the modes are Greek names).  They take a basic major scale, which has the pattern of 221 2 221 in terms of half steps.  Each mode shifts that pattern one to the left, and puts that interval that got shoved off on the the right of the list, like so:

Ionian (major): ^221 2 221 (the caret shows where the start of the pattern is)

Dorian:              21 2 221 ^2

Phrygian:  1 2 221 ^21

Lydian:  2 221 ^221

Mixolydian: 221 ^221 2

Aeolian (minor): 21 ^221 2 2

Locrian:  1 ^221 2 22

There are two ways to use that: start on the tonic note (say, D). That will use a different set of notes as you go up the scale. See https://en.wikipedia.org/wiki/.....ical_note) for examples.

The other way is to go up one note for each mode. If you do that, you will play the exact same notes as in the major (aka Ionian) mode, but you will start and end on different notes. Even though it's the same notes as the major, it will sound different to your ear.  (And of course, you're starting on a higher and higher note each time, so that's another difference.)

Those Wikipedia articles have a LOT of good information on possible scales.  You'll have to read up on some music theory (or just play them and see which ones appeal to you) to figure out which ones you might want to incorporate into your music.

There have been some good discussions on this forum about these modes, and which ones sound better for what type of music. Try searching the forum for the names of the individual modes to find them. That may help you find what you're looking for, although I think playing them may do you more good than anything, because you're looking for something that suits your tastes.  (And they're good practice.)  That wikipedia article has the specific notes if the intervals don't work for you.

The pentatonic scale is named that because it has 5 notes instead of the usual 7.  You leave out the 4th and the 7th.  The D pentatonic scale would therefore be:

D E F# A B D

The point of a pentatonic scale is that if the main piece is in the key of D, you can play random riffs in the pentatonic D scale, and they will sound good. It harmonizes well with pretty much everything in that key.  (And the same for any other key - play notes from the pentatonic scale for that key and you will fit in easily.)  

Don't ask me why, but apparently, the 4th and 7th notes are the ones that are likely to jar - leave them out and you can play pretty much anything and it will be heard as a pleasant accompaniment to the main piece. It won't stand out much, but it's great for harmonizing/being a background voice.  Anybody who wants to play with others but is concerned about screwing things up for the group should practice pentatonic scales a lot - they make you bland enough to be safe.  

Hope this helps