"What's the smallest compact 9mm out there?
If you need a pistol that will fit in your pants pocket I am afraid you will have to stick with the small .25 acp or .32acp. Bear in mind that very small pistols that are double action only are extremely difficult to hit anything with. I have an expensive Seecamp .32 that has an amazingly smooth double action pull but never the less although it is an accurate pistol off of sand bags when actually shooting it in a draw and shoot situation I usually miss silhouette targets as close as 7 yards. With a single action pistol I hit silhouette targets up to 100 yards away.
If you are looking for a low priced, reliable, accurate and small single action 9mm, look around for a used Star starfire 9mm (Star is out of buisness). It is about the same size as a Walther or sig .380 (The sig and walther by the way are excellent and comfortable carring pieces). The Star has a beveled magazine well, white dot sights, checkered front and back strap, ambidextreus saftey, all steel construction and rubber grips. There is one fly in the ointment. No gun is perfect and the Star is quite heavy at 30 ounces. But this in a way is also a virtue. The gun is absolutely controllable even in rapid fire. Try shooting a light weight sig .380 or kel tech plastic pistol in rapid fire and you will see the difference in the grouping on your target. Use the Star in an in the waist holster and it will dissappear even under nothing but a lose fitting shirt. If you want a light weight gun you might prefer the sig .380 at only 16 ounces. W.R.