He teaches Rodney to shoot straight - even on the target-range.
"It's threatening someone you care about," he says, real quietly into Rodney's ear, because years ago, that's what Jack said into his.
And Rodney gets to be a damn good shot.

The first time Zelenka mutters out loud in czech, Daniel cocks his head to one side and listens. The second time he frowns. The third time... the third time he gets up, crosses over to Radek who's fighting a recalcitrant computer and says something to him so quietly nobody else hears it.
After that, Zelenka always starts to mutter in czech - but ends up smiling.

Daniel is an explorer at heart - and he's also a very smart man. So when he starts to wonder about something, he picks up a P90 from the armory (just to be on the safe side, because Jack's endless arguments *did* make sense), and goes looking for an answer.
The third time he goes exploring, he finds the answer to something that's been bothering him for a while. Now all Atlantis needs is a hundred extra pilots or so.

About a month after Daniel came to Atlantis, he overhears a couple of thickheaded marines yammer about how good it is that there are no filthy faggots in Atlantis, and how the flyboys back at the SGC *finally* got something right.
That's the beginning of Daniel's third crusade.
He talks to Elizabeth - at length - until she finally caves and agrees to take a resolution of Atlantis law back to the IOC. He talks to the scientists on Atlatis, until Rodney, out of the blue, grabs his head, drags him halfway across the table and kisses him among half-eaten alien foods just to shut him up.
In the end, he talks to Sheppard - who's listening - and to all of the marines - who, for the most, aren't - until they surrender, just to get the hell out of the room.
And the next message from the SGC includes a unanimous ban on discriminating homosexuals in Atlantis; military or civilian - from the IOC.

On december 22nd, some five months since Daniel finally made it to Atlantis, the Daedalus arrives with a surprise on-board. Elizabeth is the first to find out, because her office is the first stop. Sheppard is second, because... well, because it's going to change his life on Atlantis. Daniel... Daniel is third, and he finds out because he's crossing the gateroom at just the right time, and looks up at just the right angle - and then he's running up the stairs, through the control-room and bursting into Elizabeths office, just slightly out of breath.
"Jack!"
An amused eyebrow lifts, then... "Daniel?"
"What are you *doing* here?"
"I got bored with Washington," Jack says, but the twist of his lips and the gleam in his eyes is telling a different story.

Thank you. I'm kinda partial to that myself... ;-)

Thank you. I think Radek needs someone on his side to make him smile more.