My big wide fry pan, baking sheets (I have like 6 lol), knives (5" Wustoff Santoku and 8" Victorinox Chef's knife), giant wooden cutting board, huge stainless steel stockpot, wooden wedge-spoon, heavy-duty steel-handled spatula, and a couple of sets of mixing bowls (two stacking ones with pour spouts and a new set of Pyrex sealables) probably see the heaviest use and I daresay all of them are used basically every week.
In terms of less-obvious ones, though. . .
Citrus Juicer - Some moderate RSI from my desk job means squeezing citrus well is tough. Lifesaver
Microplane - I probably use it more than my box grater now, between citrus zest, parmesan, nutmeg, and ginger.
Deep Fryer - Cheapo $25 GE dealio, but I fry a lot of stuff, surprisingly
Slow Cooker - I don't rely on it as much as some people, but for a few recipes, it's essential
Food Processor - I use it for hummus, falafels, gyro meat, some doughs, rapidly grating carrots and similar (I often need to grate a couple of pounds of carrots at a time for an Indian dessert I like making), and a few other things
Blender - I actually use this in cooking a lot, particularly for prepping liquid cooking sauces for stuff like chili and Chicken Tinga
Wet-Dry Mixer-Grinder - The Preethi Eco Twin my gf got me for Xmas a couple of years ago is mandatory for Indian cooking. Making chutneys, idly batters, ginger-garlic paste, etc. would suuuuuck without it