Get up... dust-yourself-off, and Move On!
The knee-jerk lawyer-up advice is asinine. The only guys who win that game are attorneys. Are you prepared to spend $5-10K+ in 'modest' legal fees so you can to go to war with a former employer? Do you really trust the courts will right the wrong you perceive?
It totally sucks being fired! The biggest bruise is to your ego and immediate cash-flow. Best to put that time/money/energy into connecting with a new, potentially more rewarding job.