f4 is seen the least since it's the worst, in the databases I can find, it doesn't even score 50%.
Would you prefere moving C4 D4 E4 or F4

I'm an e4 player, but I wouldn't mind playing d4 or c4 in a tournament (I may switch in a year or so). 1.f4 I would only play in an unrated game (club) or online if my opponent is much weaker and I'm just goofing around.

And actually, I think every first move is playable, even at the highest level. If opponents are equal and the white player has never played 1.g4 or 1.f3 well of course he'll be at a disadvantage. But right now I'm thinking the worst first move will only give black easy equality. I don't think any first move instantly puts you at a disadvantage.
I could see how many 2nd moves though could already tip the balance is black's favor.
Usually the most common that i see is E4