The g-index is a variation of the h-index.
"The g-index g is the largest rank (where papers are arranged in decreasing order of the number of citations they received) such that the first g papers have (together) at least g2 citations" (Egghe, 2006).
Unlike the h-index, the g-index is strongly affected by highly-cited items.
Egghe, L. (2006) Theory and practice of the g-index. Scientometrics, 69(1): pp131-152.
The e-index is a complementary metric to the h-index. It is designed to account for citations in excess of the h-index and provides a means for differentiation between researchers with the same h-index.
A geometrical explanation of the e-index (Zhang, 2009)
Zhang C-T (2009) The e-Index, Complementing the h-Index for Excess Citations. PLoS ONE 4(5): e5429. doi:10.1371/journal.pone.0005429