I heard you can get a cool darth vader hat by posting/commenting here, but you need reputation to post and comment, so that won't work. Are there any other ways do get it ;D
but you need reputation to post and comment
You can post both questions and answers here on Meta Stack Exchange with 1 rep (you did post this very question!) and you can post comments on your own questions and answers to your questions.
When you get the hat here, you can wear it on all sites.
You should receive the 'I am your father' hat on Meta Stack Exchange in a few minutes; you don't need any reputation to post here. Apparently, for this hat's purpose, Meta Stack Exchange counts as its own Meta.
For other sites (except Math Overflow), you'll need 5 reputation before posting on Meta, unless you post a question about your own post on the main site. That would be another way to obtain the hat. Make sure it's a good (Meta) question, though.