I'm guessing this will be the most common answer, but mine is engineer @ 121(no boosts). 7h 36 mins on the class. To find out go here - https://players.planetside2.com/#! Click on classes then check each.
Medic, though that one only has a playtime of 1H32M compared to 23H for LA and Engi so that's probably skewed. I've only got a score/minute of 60 for my Engi though.
Medic 310 score/minute (with 40% membership bonus) Engineer is actually my second worst at 136, after infiltrator 92.
Interestingly enough my Sythe, even though I don't like it as much as my reaver or mossy. My TR heavy is pretty much right up there with my mossy and reaver, only a few points off. My VS heavy is by far my highest infantry SPH, even higher then my SPH for mossy and reaver, Orion is really, really good. My NC heavy isn't on the same level as my VS and TR guy, the default NC LMG is so inferior to the other two factions it's crazy.
71.8 infiltrator. Lol no wonder I don't seem to get any certs. Scratch that. Best is max with 143 but with whole 23min of game play! Infiltrator is just 69 score / min. That's pretty bad.
151 with the LA, but I don't don the jetpack very often. I average about 110-120 otherwise. Finding something to shoot/support seems to be my biggest problem in game.
well i don't care one bit about scores + spend alot time afk. medic 242/m 1h 16m LA 137/m 40h 34m HA 147/m 8h 27m engi 159/m 71h 55m max 180/m 2h 43m inf 126/m 55h 12m for fun. VS HA with 99% lasher 130/m 22h 58m