Jazz Jackrabbit 2 Plus (JJ2+) adds countless features and bug fixes to both Single Player and Multiplayer gameplay within JJ2, and is used almost universally by most serious players. It has much better network code than the original game, adding console commands to online games, fixing most major game-crashing errors and connection problems, allowing permitted clients to log in as "remote administrators" in someone else's server and control the gameplay, and adding several new multiplayer gamemodes. It additionally fixes or enhances many of the events in the game, and allows level designers far more power than in regular JJ2 through the addition of an easy-to-use scripting language. JJ2+ takes everything great about JJ2 and adds so much more on top of it; it is truly a must-download.
Jazz Jackrabbit 2's thousands of sprites are stored in a single file "anims.j2a". For the first time, JJ2+ version 5.0 lets you import sprites from your own homemade .j2a files to really charge up the gameplay experience. In this homemade level using a homemade tileset, a mutator (a script run by a server, not by an individual level) replaces the ordinary weapons' graphics with sprites and effects borrowed from the indie game Bunny Must Die. Other scriptwriters might want to draw and define new enemies, vehicles, or anything else at all.
Jazz Jackrabbit 2 Plus v5.0 is currently available in the downloads section.