This is in answer to a request–thank you for reading!
The cross can be compared to a gun or guillotine, because it was an instrument of torture, a mode of execution. Yes, a symbol of shame. Because Jesus took our sin on Himself–he took our punishment for us. This was the only way that we could have a relationship with God, since He is holy (meaning absolutely perfect)–someone had to pay the price, and it had to be someone who had no sin of His own to pay for.
Actually, in Biblical times, never mind that previous paragraph–it just was a symbol of shame and torture, for it was the way they executed their criminals.
Hope that helps!