Have very fond memories of playing J2ME games. Here's some off the top of my head: Zombie Infection (what a great game!), Galaxy on Fire, Sims, Age of Empires, Real Football, Orcs&Elves, Pokémon Crystal on an emulator...

And of course a limited port of Worms Armageddon that has to be one of the games I sunk the most time on, seeing as I played several matches a day with my friends for an entire school year! Ahh I even scribbled a "campaign mode" on my math notebook during class instead of paying attention!