Some ideas I came up with:
"Crota Woman still droning on?"
"Eris put [i]her[/i] rock, on my map. [i]My map[/i]. It's bad enough that you guys walk all over it to begin with!"
"I'm still not telling you about that girl's name Guardian."
*Whispers* "Don't leave me! You're my only connection to the outside these days!"
"First, I lose a bet. Then, I lose my freedom. Guardian, learn form this and don't sign up for the Vanguard."
"Think Zavala would mind if I left the Tower for a few days to, uh, scout around? Yea I though not..."
"Hey, is Amanda doing anything right now?"
"If you have anything interesting to say, say it now because my attention span's been functioning at 0.04% today."
"Zzzzzzz-zz- Wha- What? Sorry, I was taking a well needed nap."
"I feel my sanity slipping everyday from listening to Ikora's boring talks on research. Got any good jokes?"
If you got some of your own, feel free to post them.