We've all saved/destroyed Goodsprings and helped Jason Bright find his creator, but what about those unmarked or smaller quests that you may have missed on your first playthrough?  For me, it was the Coyotes (started in Aerotech Office Park), I won't spoil the story for anyone that hasn't done it, but it was a fun little quest.

the atomic wrangler quests are pretty fun and i always forget to do them

I really enjoy the quest where you get the high-end hotel room at the Tops when you gamble a lot. On top of motivating me to win at the tables, I get to hang out in the sweet room with all the caps I've won

Restoring Hope (the quest in Nelson) - where you have to "deal" with the captured troopers. I thought it was interesting and offered a very open ended playstyle (follow through & kill, take the moral high road, etc.)

I missed the Barton Thorn quest my first playthrough but on my second I found him and after he told me his sad story, I just had to help him. I died several times fighting the geckos and used most of my stimpacks and when I got to the top and he came up there and told me he lied and was going to kill me, I got to mad and killed him. I was so upset that I wasted all my time doing that just to get a crappy 9mm off his body and a few mines out of a box. From there on, I killed him on sight and looted his ammo and gun to sell. Even though it caused me so much anger to do that quest, it still was a cool unmarked quest that I enjoyed doing.

I haven't even heard of half of these quests. One notable one for me though was retrieving Ranger Morales' body.

That's one that alot of people just skip over and honestly I did too when I played on Console.

I guess not too secretive, but the cave quests the doctor at Bitter Springs gives you. I never hear anyone talk about them, even though it's a 'clear the cave or negotiate for the goods' quest. I actually learned I don't hate all caves equally after entering those lol...I made a personal home out of one once I finished the quest.

Uhh the Ranger Andy unmarked quest i could have used that perk in a lot of battles and you have to do somethin or other to ask you to check on the camp