Serpent Audio SB4001 by chinesewhiteman
The SB4001 is a fantastic bus compressor. I do not know if it's really like x, or y, because I'm no bus compressor guru, but I love this thing on drums and master bus duty. It's very flexible, but I usually grab it for snap and mid forward tone. It gets down right AGGRESSIVE while not getting harsh and somehow staying transparent, if that makes sense...
Extra points in the features category for having mix, "grind," and plenty of side chain options. All of which are excellent and extremely useful to have. (Grind being fairly subtle, which is a good thing)
Easy to use for those who know their way around a compressor.