cl_trypants was imported by me. Created by a friend of mine, one day he told me to put on my try pants... And there it is lol. I mostly use it, but others use it too, it's a fake command that does nothing but brings out a good laugh or two.
Also if your team is doing bad try setting cl_suck to 0 :-P
If you're a sit back and wait kind of guy try engi. A bit complicated at first but they sit back and wait mostly... Again a bit complicated but they are a good sit back class, just watch for spies.
A sniper is also like that, but unless you're really good, i'd try only on some of the more "open" maps.
A medic is a support class as well but they are more into the battle. Run with your teammates and heal who's burning or inured, leach onto a soldier, demo or pyro... But mainly a medic is a heavy's best friend... And just try not to die.
Those are your support classes

Then again some others can be... i've been a heavy, sat by an engi's dispenser and just spammed my minigun to make sure spies aren't in the area... Pyro's sometimes do it too.
Just fool around, see which one fits you best.