[CutiePie2000]

We must have a psychic bond, because I was thinking this yesterday!

Alpha and Delta seem to get used a lot, but Omicron, Xi and even Psi, Eta, Iota not so much.

Omicron: I can only think of AOII.
Xi: I think only AXiD and Theta Xi use it.
Mu: I can only think of Phi Mu and Sigma Alpha Mu, but surely there must be others (I am just too lazy to go and look).
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At my campus, we seemed to like Alpha, Delta and Gamma and Phi!

Alpha Gamma Delta
Alpha Delta Pi
Alpha Phi
Delta Phi Epsilon
Delta Gamma
Gamma Phi Beta
Kappa Kappa Gamma
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Also:
How many "Tri-somethings" are there?
There's Tri Delta and Tri Sigma (NPC)
There's Tri Alpha and Tri Zeta (I think they're locals).
There's Tri Kappa (I think it's educational or honor or something) and there's Tri Beta (also something along those lines).

Any others?