This is an excerpt from the usage help message:

 -M           do not demangle symbol names
 -n, -nn      do not load RBin info (-nn only load bin structures)
 -N           do not load user settings and scripts
 -q           quiet mode (no prompt) and quit after -i
 -Q           quiet mode (no prompt) and quit faster (quickLeak=true)
 -P [file]    apply rapatch file and quit
 -R [rr2rule] specify custom rarun2 directive
 -s [addr]    initial seek
 -S           start r2 in sandbox mode
 -t           load rabin2 info in thread
 -u           set bin.filter=false to get raw sym/sec/cls names
 -w           open file in write mode
 -X           same as -e bin.usextr=false (useful for dyldcache)
 -z, -zz      do not load strings or load them even in raw

Open a file in write mode without parsing the file format headers.

$ r2 -nw file

Specify which sub-binary you want to select when opening a fatbin file:

$ r2 -a ppc -b 32 ls.fat

Run a script before showing interactive command-line prompt:

$ r2 -i patch.r2 target.bin

Set the configuration variable:

Debug a program:

$ r2 -d ls