For me?

I use almost exclusively the Vic3/Mike3 figures.

I like the SP3 as well, but as someoen earlier commented - VERY hard to 'un-steph' her face. Extremely difficult to make her face look original. Also very little vendor or freebie support in comparison to the M3/V3's.
Beyond that, I still use my Posette and my M2/V2 figures from time to time as well. Also the Generation 2 kids. (NOT Gen 3's)

But for me, I think the M3/V3 figures are my fav...

Have Aiko - can't stand her - never use her.
Don't have E-Frontier's stuff
Don't have apollo
Don't have...etc...

~ Seliah