Whatever is in the fridge really, usually prefer chicken but beef goes alright.
Usual suspects of vegies, broccoli, capsicum, mushroom, carrot, cauli, baby corn
Just fry off some onion, garlic, ginger. Throw in the meat for a few minutes, then pull it out into a bowl. Veggies in till they're cooked, then meat back in. Bit of sweet chilli, kecap manis, soy, maybe a splash of fish sauce if there's some there. Job done, serve with steamed rice or heat up some egg noodles and throw them in.
Making my hungry just thinking about it!