I'm not a MCA veteran but heres what I have been using for last couple of years and they are amazing.

Ondeck
Rapid
Knight Capital
CDG
Fox Capital
Global Funding Experts
Lendini/Funding metrics
Everest
Vital Cap
Fundworks
Lendig Valley
Total merchant
BHB Fudning
River Advance
CFG
Velocity
Legend
Fundfi
YSC
LCF
Cooper
Bitty
GMF (they are broker)
Credibly
Queen