Putting my few ha'penth into the mix...
I used to use AA Fields, but found that JSB RS grouped better. Odd, as I never got on with JSB Exact or any other 'short' pellet for that matter.
Recently I have tried Bisley LRG. These are worse than the RS out to 30 metres, but better at 40, which I don't understand.
Never got on with H&N FTT, RWS Superdome, Accupel, Accupel FT. I use an AA Ultimate Sporter. I know many others rate these pellets, but as always it's what your barrel likes.
The problem with being old is that you can remember when things weren't crap. Sometimes.