Make it so we can up-vote another user's comment on chat. Like up-voting, except we get no points for it. It will be a fun way of saying: Hey, that's funny! Also make it so there's a cute little thumbs up too!
Another could be that if you're feeling happy, you can put a little smiley face next to your name and same if you're feeling sad, etc.
Also put Swaggron's suggestion about the little pen thingy.
Here's the big one. On your profile, it gives you a place to enter your birthday. When that day comes, instead of having to look a wee bit obnoxious yelling "IT'S MAH BIRTHDAY!", there's a little party hat or birthday cake next to your name everywhere. So people can go and see it's your birthday. ''Hey Rio, happy birthday!".