olives - i buy massive jars from lidl, drain them then dry them off in a tea towel overnight, then layer them back into the jar with sliced garlic, sliced chillis and a top up with evoo mixed with a couple of teaspoons of chipotle paste. Everyone, even folks who hate olives, seem to like these and because they are always covered in oil they don't go off. Not that that is ever really a problem! 
green peppers - again I would stick blend and chuck in with bolognaise or any other pasta sauce or stew, although once they're roasted with the other peppers and garlic evoo I don't think they're really that noticable, and i second the suggestion of mixing them in a curry, I think they lend themself to curry.
yes, yes, yes to freezing lemon, limes and oranges that are a bit tired, for use in gin and tonic to stop the ice from watering it down!
Bananas, even pretty brown ones, get bunged in freezer in skins until i have time to make a banana cake/muffins with them, or my ds favourite use is in a berry smoothie. buy frozen berrys, bung in a frozen banana dash of orange juice and some yoghurt, yum!
Also cook and freeze potatoes mashed and sometimes mix with leeks sauteed in butter. Also bulk buy leeks when on offer in Aldi, slice and saute in butter then freeze. You can just hack some off the block and use in quiches, sauces, soups, anything really.
However, we do have chickens so plate scrapings and the occasional scientific discovery at the back of the fridge always get used up.