bench presses: they are heavier/harder than pushups, at least for the pecs. Pushups are good ab work, and obviously a more whole body exercise, but I like the heavy, heavy weights squishing me into the bench. I like knowing my chest is strong.

bicep curls are just for having strong biceps, not for any other cool move -- some of my friends call them beach muscles, but it's funny, they never say that when i'm helping them move boxes in and out of their apartments. :)

hamstring curls... well, I have heard that they're not as useful for other activities as other exercises that use the hamstring to move the hip joint. I like them though. They've made my knees feel more stable in positions where I'm holding a leg out behind me and straight, which used to (and sometimes still do) feel sort of dangerous/wobbly around the knee. If I were strong enough to do glute ham naturals instead, I probably would; but I'm not, and I do back extensions, and yoga, both of which use the hamstring to move the hip.

I highly recommend squats. Warning though: they felt awful to me for four months straight before finally, the seventeenth week, I loved them. So, only if you plan to stick with them. Also, they don't do a damn thing for jumps since they teach you to move fastest in the middle of the movement and slow again at the end.