The mother of all boot flags. Entering -v into the bootloader turns on verbose mode, which is absolutely critical for fixing any Hackintosh issue. Verbose mode displays every single process that takes place during your bootup of Mac OS X. It can be rather intimidating, as it will display hundreds of lines of commands during the bootup process. However, if your Hackintosh isn't booting, then verbose mode should freeze at the exact point where the bootup process is tripping up. Take a photo of what verbose mode says before the bootup freezes and please share your pic before asking for help on the comments box.
Turns on safe mode. Mac OS X in safe mode ignores all kext files and boot settings except those which are absolutely necessary to booting the system. Safe mode is useful if you're trying to run the Mac OS X installer on a PC that's not fully compatible with Mac OS X. Also, if you accidentally installed a kext file that's messing up your Hackintosh, booting into safe mode may work around the problem. In safe mode, you can then remove the offending kext from /Extra/Extensions in your main hard drive (if you're running Mac OS X Snow Leopard), or /System/Library/Extensions (if you're running Mac OS X Lion or Mountain Lion).
If you've entered some extra boot flags into org.Chameleon.boot.plist, but they're messing up your Hackintosh's bootloader, enter the -F boot flag to ignore them.
Ignores kext caches during bootup on Mac OS X Snow Leopard. If you did not install a kext properly (usually because you forgot to run System Utilities in Multibeast after installing a new kext), your kext cache will be damaged, and Mac OS X might become unbootable unless you use this boot flag. The kext cache was replaced by the kernel cache in Mac OS X Lion, so theoretically, the -f boot flag should no longer work; however, this boot flag can still help some Hackintoshes boot (for reasons unknown).
Mac OS X Lion and Mountain Lion can use the kernel cache to install kexts, allowing Mac OS X to boot faster. However, the kernel cache is turned off by default, and you have to enable it by using the boot flag "UseKernelCache=Yes" (without quotation marks). Installing Easybeast or UserDSDT with Multibeast will automatically turn the kernel cache on for you. If Mac OS X is booting extremely slow on your Hackintosh, the kernel cache might be malfunctioning, and you can turn it off with "UseKernelCache=No" (without quotation marks). Turning off the kernel cache is equivalent to using the "-f" bootflag in Snow Leopard.
Some Hackintoshes will only boot when their "PCI Root ID" is set to 0. This usually happens with Hackintoshes that use a AMD Radeon graphics card. Other times, a Hackintosh will only boot when its "PCI Root ID" is set to 1. In some cases, the boot flag "PCIRootUID=1" will also fix Mac App Store verification errors.
If your verbose mode bootup of Mac OS X Lion or Mountain is freezing at [PCI Configuration Begin], enter the npci=0x3000 boot flag to fix it. This flag is applied by default when you install Easybeast or UserDSDT with Multibeast. The boot flag npci=x2000 does the same thing, except that it only works for Lion.
Forces Mac OS X to boot into 32-bit mode. Sometimes, your CPU or graphics card won't be fully supported in OS X unless you boot into 32-bit mode. Unlike in Windows, booting the 32-bit kernel for Mac OS X does not limit your total amount of RAM to 4 GB, and you can still run 64-bit applications. However, single applications cannot use up more than 4 GB of RAM, so this is a disadvantage if you do professional video editing, or something else that takes up a lot of RAM. This boot flag no longer works in OS X Mountain Lion.
Allows Mac OS X to boot into 64-bit mode. This boot flag is usually unnecessary, as Mac OS X Snow Leopard (and all versions beyond it) will boot into 64-bit mode by default.
Forces Mac OS X to boot into 64-bit mode. This is usually required to boot AMD Hackintoshes, especially on Hackintoshes with AMD's newer six-core processors. Interestingly, you can use the -force64 boot flag and the arch=i386 at the same time (I'm not sure what this will do, though).
This boot flag limits Mac OS X to using one core of your CPU. This boot flag is often necessary to launch the Mac OS X Snow Leopard installation DVD on a Hackintosh with an unsupported processor (ahem, AMD processors). However, you shouldn't have to use this boot flag once you've installed the legacy kernel.
The 20 is replaced with your CPU's bus ratio. This boot flag is usually used when you're installing Mac OS X Snow Leopard on a processor that's not supported (once again, AMD processors). Snow Leopard supports more processors than it used to, so this boot flag isn't as common as before. You can find a list of busratios for 2010-model Intel processors here. You can also find your busratio manually.
This boot flag locates the kernel ("mach_kernel"), an important boot file for Mac OS X. If your Hackintosh's verbose mode says that it can't find mach_kernel for some reason, entering this boot flag will help the bootloader find it (the kernel is usually found at the very base of the OS X file system). If you actually moved your kernel to somewhere else in your hard drive, change "mach_kernel" to wherever the kernel is located. For example, if the kernel is in the Extra folder of your main hard drive, enter the boot flag "/Extra/mach_kernel" (without quotation marks).
This turns Graphics Enabler off/on (you can set "No" to "Yes"). Graphics Enabler is a feature that helps Mac OS X work better with your graphics card, so it's turned on by default when you set up your Hackintosh with Multibeast. However, when used with certain graphics cards (especially AMD Radeon cards), Graphics Enabler may make Mac OS X unable to boot, or cause the graphics in Mac OS X to display incorrectly. If this is the case, try entering "GraphicsEnabler=No" (without quotations) instead. Turning GraphicsEnabler off will break DVD Player, as well as Geekbench, most games, most video editors, and certain other apps. Graphics cards from NVIDIA's 600 series no longer require GraphicsEnabler to work with Mac OS X; in that case, turning off GraphicsEnabler won't cause any negative effects.
Turns on debug mode. If you use either of these boot flags, and Mac OS X gets a kernel panic (which is the Mac version of the blue screen of death), you'll see a debug screen full of code instead of a generic "You need to restart your computer" message.
The DarkWake feature in Mac OS X Lion and Mountain Lion allows you to wake up certain parts of your Mac from sleep, while leaving other parts in sleep mode. Unfortunately, this feature often messes up sleep on Hackintoshes. Enter this bootflag to turn it off (enter darkwake=1 to turn it on, if turning it off doesn't do the trick). Additionally, if your verbose bootup is freezing at a bunch of commands that mention "SleepEnabler.kext", entering darkwake=0 should be able to turn SleepEnabler.kext off. (Once you boot into OS X, be sure to remove SleepEnabler.kext completely by deleting it from either /Extra/Extensions or /System/Library/Extensions in your hard drive.)