In no particular order:
Keepers - they're scary when they're out there and doing their thing
Harvesters - Again, when doing their thing properly, a well role-played Harvester can induce nausea and fear in bio-units. (I don't think the guys in New Berlin liked my description of just HOW we 'process' bio-units.)
Wilde - nice guys to meet over a gunsight
SCRA - Comrade, we must have vodka!
BHG| / BHG|Core - remember, we're (trying to) keep the lowlutters out...
Order| - Defenders of Humanity - yeah, right, we'll meet you on the battlefield
BPA - Tip a cuppa tea to these guys
LPI - Never have so many taken so much abuse from so many for so long
CR - I don't get up that way very often, but the RP I've always had with you guys has been good
Benitez, OPG - You Corsairs aren't all the same, but you two are the best of the scum... :P
Note that I'm only in TWO of factions listed - I'm not in all the groups like many of you are. My positive feelings towards these factions is due to my interactions with them over time with all my characters.