How about the joke about Joker? The first time after you have the nightmare you go up to the bridge and Garrus and Joker are at a 'Joke War' xD
1. Garrus: Alright, Whats the first order an alliance commander gives at the start of combat?
Joker: Uhm...I give up.
Garrus: (laughs) Correct.
2. Joker: (laughs) Alright big guy. What do you call a turain gets killed by a horrible spiky monster?
Garrus: Friendly fire. Come on! That one goes back to Shenshi.
Joker: Eh, you gotta respect the classics.
3. Garrus: How many humans does it take to activate a dormant mass relay?
Joker: 602. 600 to vote on it. 1 to ask the Asari for technical help. And one to request a seat in the council afterwards.
4. Joker: How do you know when a turian out of ammo?
Garrus: He switches to the stick up his a** as a back-up weapon.
5. Garrus: Why does the alliance hire pilots with bridle bone disease?
Joker: Your- your shitting me! The turain military has one about me?
Garrus: Oh! Well absolutely. I heard it myself from a privet back on Palaven.
Joker: Alright, why does the alliance hire pilots with bridle bone disease?
Garrus: So their marines can beat someone in hand to hand drills.
6. Joker: Pfft! Damn you need to tell James that one. Hey whats the hardest part in treating a turain who took a rocket to one side of his face?
Garrus: Figuring out which side took the rocket.