Lost in Nightmares is short, but SWEET.
And I have way too much fun playing Barry in Mercs, Excella's gun critical rate is pretty insane too, quite easy to score high.
It's only easy to score high because of the amount of mini bosses the game tosses at you.
Also, Jill's gun, the Px4 is the ONLY gun to have an extremely high critical chance of headshots at 87.5%. Excella uses the M93R which doesn't have any special attributes (though it does have the DEFAULT chance of a critical hit), but that coupled with 3 round bursts makes it seem like it has a high %.
Gun stats are posted the American RE5 guide.