i have a bad habit of saying 'you too' as a response to people. for instance, when people say 'have fun in the bahamas!' i'd reply, 'you too! i mean... thanks!'
other examples include:

gate attendant
'have a nice flight!'
'you too!'

my manager
'good luck in school this year!'
'you too!'

waiter/waitress
'enjoy your meal!'
'you too!'

the only time i ever say 'thanks' is when people insult me. ironic, eh?