Ugh, Technic and tekkit has some kind of weird TooManyItems. It doesn't have the creative/weather settings and I can't actually use it to get stuff.
It's Not Enough Items; press the 'o' key to hide it. You can also go to the options by clicking the Options button in the bottom-left corner to set the configuration of it (such as Cheat and Recipe mode, and additional cheats (the buttons)). Item spawning in SMP is identical to Too Many Items, in which you need to have permission to spawn items in the first place, and the chat command must be changed if you're on a server with Bukkit and the Essentials plugin.
And in SSP technic there's A LOT of human enemies in armor and with bows. I can't go anywhere without getting show down by a mob of them, what the hell is this.
Sounds like either Humans+ or that wretched Tales of Kingdoms mod. Both are not worth the hassle they cause, IMHO.