Most ADs I've taken contributed to hypo/mania and rapid cycling at some point or other - Effexor, Zoloft, and Prozac (which was the worst, bar none). Wellbutrin has been pretty good for me, for a very long time, but I'm adding Lamictal now in hopes that it will even things out a little.

Lamotrigine is cheap, my copay is $3 for 60 25mg tabs (20% of retail cost). Bupropion XL is not quite as cheap but not breaking the bank; my copay is closer to $25 for 90 150mg tabs (again, 20% of retail because it's a generic.)