Do you know any useful mathematical constants that I can program into my calculator?

[Peter1986]

One thing that I have always liked a lot about scientific calculators is that they often allow you to program values into letters - which is very useful for various annoying mathematical constants etc, plus it tends to conserve a lot of space - and I was wondering if you know of anything nice that you would suggest that I should plug into my calculator?
This is what I have got so far, expressed in SI units:

C = 3e+8 --- (speed of light)
E = 1.602e-19 --- (magnitude of a proton/electron charge)
F = 0.3048 --- (foot/meter converter)
G = 6.674e-11 --- (gravitational constant)
H = 6.626e-34 --- (Planck's constant)
I = 0.0254 --- (inch/meter converter)
J = 1e-12 --- (sound intensity for 0 dB)
M = 5.97e+24 --- (mass of Earth)
N = 6.022e+23 --- (Avogadro's constant)
O = 6.371e+6 --- (radius of Earth)
R = 3.29e+15 --- (Rydberg's constant)

Do you know of anything else that's cool to have, or anything that I should replace with something else?
In that case, do post your suggestions, and I shall be grateful indeed.