I use a few words to say hello, such as 'Hey', 'Yo', 'Ey up' and 'Alreet' (a local thing!). I rarely say 'Hiya', and even 'Hi' sounds a little 'puffy', if you see what I mean. Maybe that's just me.
How about different ways for goodbye? Normally I say 'See ya', 'See ya later', or just 'Later' and on emails 'TTFN' or 'So long for now' or 'Catch ya later'.
I often used to say simply 'Bit' (short for 'See ya in a bit') which was something of a Simon-ism that didn't really catch on. Pity! :-(