1. Jazzopoly! Fun, simple, cooperative (no losers, no required skill level), shows what modding/jj2+ can do: https://www.jazz2online.com/downloads/7606/-/
Problem is that the .zip contains TopSecret.j2t, but the level uses Top Secret.j2t (with a space) So this should be fixed first. Second problem is that the level does not work with splitscreeners, you have to play in a server for it to work too. Nonetheless great level.

2. Anniversary bash pack. Quick and easy way to obtain a bunch of high quality Battle and CTF levels