Trinity/Revtech, Reedy, EA Motorsorts, SMC, OHP, Thunder Power, Orion.
Pick any of them, they are all great. There are a lot of conspiracy theorists out there but its really hard to buy a bad LiPo pack now-a-days even if you get cheap ones.
What I run: Schumacher Mi5/Associated RC10R5.1/Associated RC12R5.2/Futaba/HobbyWing/Team EA Motorsports/BSR Racing
Where I run: Florida Indoor R/C Complex/Thunder Racing/Florida On Road State Series