Use a Minimalist HUD

[www.teamfortress.tv]

HUDs don't affect performance, this test shows 1-3% FPS difference. However, the stock HUD covers a lot from the screen and has an unfriendly layout. Using a custom one is advised to have less visual clutter and they can have bonus features like showing the last damage and other health information.You can find many at http://huds.tf/