What can you get with good karma on fallout 3

Good Karma can provide both positive and negative effects.

Postive effects:
-You can recruit Star Paladin Cross & Fawkes as companions
-Megaton Settlers may come up to you and give you small rewards (eg. ammo)

Negative effects:
-Talon Company Mercs will spawn at certain locations and attack you

Other effects:
NPC's may comment on your good karma (eg. Three Dog On GNR)