My group - Chaos, Mayhem, Havoc & Turmoil - took on the Guardians Citadel with nothing but kevlar armor and rockets (LAW and Sabot). Pop from behind a corner, light off a round, pop back behind the corner.
So, I essentially blew thousands and thousands of dollars (and had to load many, MANY saves after the entire group was massacred)...only to find out some time later that I REALLY should have discovered Sleeper Base first.
On the upside, the rest of the game seems really easy once you have Power Armor very early in the game.
Then, there's the time that I lugged a dead NPC recruit (his name is forgotten) around for days before noticing that he was, in fact, dead. I took him to the Citadel, gave him a robe and a spear, then buried him by one of those warning flags.