I think StarGrunt II is a good one i been playing it on and off for years i started out using 25mm then went to 15mm as theres loads of scifi 15mm around now. it plays really well but it is a little counter heavy but it does help with the game flow as you rarely need to look anything up any question sent me a message if you want i can help you with any rule questions and i have loads on my own tank and walker designs