Caffeine, ashwagandha, schizandra (based on Russian research), pycnogenol (studies show increased cognition in students, as well as athletic improvements in soldiers), Phosphatidylserine (PS) and Alpha-GPC (other forms of choline as well) come to mind, as they have research showing benefits in at least some aspect(s) of athletic performance.
Other supplements can improve athletic performance by increasing energy or focus or reducing fatigue, stress or anxiety, but that's a little more indirect, and these don't improve athletic performance per se I think. Things like ALCAR, rhodiola, and ornithine come to mind when I think about reducing fatigue, which could help you athletically if your performance is limited by physical or mental fatigue. Things like ALCAR, huperzine, and racetams can also help with focus, which I suppose can improve athletic performance.
I don't know if I'd say that taurine is really a nootropic, but can "neutralize several untoward effects of caffeine excess," is dirt cheap, and can slightly increase endurance.
Blueberry extract can also accelerate muscle recovery, and actually "induces cellular adaptive events that serve to accelerate muscle repair and recovery of muscle isometric strength," and, on a somewhat related note, although I don't think I'd consider pomegranate extract to be a nootropic, it has been shown to increase blood flow and endurance.