If you are new at modding try mcpacher and modloader. Once you get them to work then you install x-ray mod and if you want better trolls visit www.wizardhax.com and there use freedom hax or nodus.(note you can not use both at the same time.).
most people have herd of CALL OF DUTY, but not the mod part. People mod call of Duty for faster rank, more kills and for trolling. A way that a person could troll on a Call Of Duty game is with god mode(this is where you cant die). A person with God mode can stand in front of an apponent and not let him move. or he/she cold have invisibility mod where you can turn invisible and stalk the apponent and then fallow him(or if you are in a costom game where it is you and your freind you could troll him with invisibility).
In garrys mod you can mod too. Garrys mod is the easiest game to mod in, all you do is extract and copy and past. And the mods are almost allwase working, like god mode and noclip and allmost evey other out there. Garrs mod dosn't have as much mods as minecraft but it hase a fair amount. In garrys mod, if you are playing ,conter strike, or ,half life 2, you can troll with noclip by walking thrue the walls.LOL.=D.