Modding Call of Duty: Black Ops on Xbox 360—whether through JTAG/RGH hardware exploits, modded lobbies, or aimbot scripts—is strongly discouraged. The consequences range from permanent account bans to physical hardware damage, and the "benefits" ruin the experience for everyone else.
Black Ops on 360 has huge replay value without a single mod. Invest your time in skill, not risk.