Are there any global key combinations suitable or specifically reserved on OS X for user assignment? I'm trying to identify an appropriate global hotkey to set in iTerm2's preferences for showing/hiding it:



I'd like to avoid any conflicts with other applications' hotkeys or other future use. Are there any blocks of key combinations reserved for user assignment in OS X, or groups of key combinations which aren't generally used, which would be particularly suitable?
Here are Apple's official OS X Human Interface Guidelines for Keyboard Shortcuts. 

The document appears to be a current, authoritative, and complete guide to assigning keyboard shortcuts. It covers both the conceptual basis for using particular modifier keys, as well as the nitty-gritty of exactly which keys and which combinations are reserved system-wide, or likely to be reserved in the future.

Here's second Apple page showing a complete summary of existing keyboard shortcuts.