/spawn - Teleport to spawn
/unguest [player] - Invite another player into the server, gives them regular member permissions. Please do not unguest users you do not know, this system helps prevent grief!
/sethome - Sets a personal warp to your home. Lands also have accessible warps I think
/home - Go to the location you used /sethome
/playerwarps - Setup a warp that you can invite other players to
/cluescrolls - Purchase challenge scrolls with XP for special items
/tpa - Request to TP to another player
/sell - Sell what is in your hand, your entire inventory, or your blocks
/balance - See how much money you have
/baltop - See the top earners on the server
/chestshop - Setup locked chest shops to hawk your wares. There are slots at spawn if you want to have easy access to customers, otherwise you can make these anywhere.
McMMO adds skill trees, abilities, and ultimates to Minecraft.
/mcmmo help - Explore other McMMO commands
/mcstats - View your McMMO stats
/[skill name] - Get stats and available abilities for a given skill