The Model 10 would qualify as a very common all-around simple design with a great trigger and excellent inherent accuracy. Prices are rising on all older Smiths, but it shouldn't be tough to find a Model 10 in excellent shape for $500 or less.
In fact, for that budget, I would look at the S&W K-38 Masterpiece revolvers, which were K-frames .38 Specials like the Model 10, but with adjustable target sights, nice checkering, a smooth action, and many had target hammers, triggers, and stocks also. These were the Model 14 (6" barrel) and Model 15 (4" barrel). They are excellent and affordable, but prices continue to rise.