I noted that Agent Preston, a regular cast member in Deadpool the last few years, showed up in the first issue of Black Widow. Which means Preston has reached that level of, prominence, status, something, where she's a known SHIELD agent that shows up in books from time to time.
There have been a lot of those, as the stars of different ones rise and fall depending on who is writing a lot of books for Marvel at the time. Sharon Carter and Dum Dum Dugan, obviously, but others like Jimmy Woo, Clay Quartermain, Maria Hill, Fury of course, and a bunch more I'm forgetting or just not bothering to list here.
The question for the day is, which SHIELD agent is your favorite? It can be any of them you'd like, although lets base it on their actual work for SHIELD. I really like Jimmy Woo, but it's because of Jeff Parker and Leonard Kirk's use of him in Agents of Atlas, where he wasn't exactly a SHIELD agent. So if you're going to say Dugan because of his time as a Howling Commando, no.
For me, it may well end up being Preston before too long, but for now, I think I'll take Derek Khanata. It's that Agents of Atlas connection again, but Khanata has an interesting career considering he was recommended to SHIELD by the Black Panther himself, he ran the new version of Scorpion (the teenage girl one Greg Pak and Fred van Lente created) as a sort of double agent against AIM. Even if I didn't like him a lot there, because he was using a homeless orphaned teenage girl, he did have her back when she needed it. He's willing to play a little dirty, but on the whole, still seems like a honorable guy trying to do the right thing for his agency, his friends, and his family. I can work with that.