Everybunny is different.
I don't think cucumber is recommended for other reasons - and for the record, NONE of my guys will eat it -- but other than regular cautions aboutthe cabbage/brassica family like cabbage, broccoli, caulitflower, kale, brusselsprouts, etc, MAY have higher instances of gas, it's pretty much a crap shoot.
Dill gets terrible gas from cilantro (of all things), I think Jordon got it from bok choy, Radarfrom collard greens. (Nobody was all that happy with me or the gas gods when they got an almost all-brassica meal by mistake).
My bigger bunnies eat peppers (the little guys think I'm insane for offering),it's never caused gas.
The key is volume (so they don't eat something they may have second thoughts about), variety (feed from differentvegie groups), dilligence re:rotting bits,and easing into new or rarely-fedveggies.
sas :bunnydance: