we are pretty good at getting a full lobby, as most of my friends have halo reach. we play a lot of hot pursuit maps, and i am usually the host. i have so many custom games, it takes me a few minuets to find one map. halo 3 classics are always good, (halo on halo, frogger, dodge ball, rainbow road, ice cream man, sacrifice, and of course 5 chambers, ext.) there's also infection, race maps are always good when you have a small lobby, or im just playing with my friends. i love the new insane gametype as there are so many options. hog potato is a great custom game where its like king of the hill only a warthog is the hill. each player has 2 sticky, and a grav hammer. jump rope is good, its sort of like funslide/speed only opposite,where the zombies try to spatter you, and you can't move, only jump. a good game to play with 2-4 ppl is achievment horse maps on forge. invastion is also a favorite for big lobbies. undead village and not another ambush are good.
sorry, if i just put a randomly jumbled list. like i said i have a huge amount of custom games, and so i ended up just listing on. i could make a list a mile long, but i think that would be too much. anyway, if you want to play some great halo reach custom games, or figure out what some of the games i mentioned are add me, GT agent sensi foo.