There are plenty of very good friendships between heroes. I thought of starting a thread for them. But then I thought it'd be more fun to hero friendships with non-costumed parties. No love-interests allowed - platonic friendships only.
Jaime Reyes with Paco & Brenda - From the 2006 Blue Beetle series. I absolutely love these three.
Bruce Wayne with Jim Gordon - It's a classic.
Bart Allen with Preston Lindsay - From 90s Impulse title. These two are a lot of fun.
Honorable mention to Clark Kent with Jimmy Olsen - I like the idea of these two a lot, but finding an era where Jimmy's not written like a doofy loser, Clark isn't dismissive of him, I actually like the storyline, and they actually interact is more difficult than it seems.