Will you be using Nvidia gpu? If so BenQ XL2420T Professional Gaming Monitor
This is one of the best 2D and 3D 24 inch monitors available with a 120 Hz refresh rate, 2m response time, and Nvidia 3D Vision 2. Gaming mode presets can easily changed based on the game you're playing.
If you prefer IPS gaming monitors i'd recommend Dell UltraSharp U2412M