Wet 'n' Wild liquid eyeliners, hands down. The H2O Proof lasts all day and comes in great basic colors, the regular Mega Liners last ultra long as well and come in fabulous colors like purple and peacock green. Both last all day no question if applied over UDPP as a base on the lids. Even in the nasty AZ heat they look freshly applied after 8 hours! H2O Proof is $3.99 and regular Mega Liner is $2.99. The H2O Proof comes off easily with an oil-based remover.
You can look at basically any of my FOTDs to see what they look like in real life, I have nearly all the colors.