I'm using the PMV16XN MOSFETs with 3.3V signals.
Vgs(th) = 0.65V, Rds(on) at Vgs = 2.5V and 6 A = 18 mOhm. USD 0.48 a piece on Mouser.
The FDD8447 is much more expensive at $0.85 (but can do 21A instead of a mere 8.6A for the PMV16XN, and it's big brother FDD8447L_F085 even 54A).