-f                            Force rebuild extensions cache
-v                            Verbose booting shows debug information
-s                            Boots into single user mode (means only terminal based mode)
-x                            Boots into safe mode
-legacy                       Boots into 32bit instead of 64bit mode
rd=disk0s1                    Force to boot a specific partition on a specific drive (BSD drive notation, means disk0 = physical disk 1). Here disk1 partition 1 is forced to be booted.
Graphics Mode=1024x768x32@75  Forces to boot with a resolution of 1024 x 768 with 32bit colors at 75Hz
Kernel=mach_kernel            Forces to load a specific kernel, helpful for testing of new kernels.
cpus=1                        Force using only 1 CPU core, may help addressing issues
idlehalt=0                    May solve stuttering and shuttering on dualcore CPUs
platform=X86PC                Forces to not use powermanagement (disables ACPI)
platform=ACPI                 Forces to use powermanagement (enables ACPI, but may crash your system)