In MMORPGS... Follow a high level player around asking for money... over and over. Request a duel from someone weaker than you repeatedly. Dance on the bodies of any monster you KS Choose a very short character with a very large weapon. Then win in pvp because no one can target you with a click.
In FPS... Use only a rocket launcher and a fast melee weapon. Always use up your rockets first on anybody more experienced, hopefully blowing yourself up on the process, and ending their kill streak. If you live long enough to run out of ammo, break windows until somebody gets mad.
In Fighting games... Pick the joke character and run away as your opponent tries to catch up with you. (If there is character creation) Make a very muscular character with chest hair. Now mount the most ridiculous piece of headgear upon his head (I prefer a deer head, but if that is unavailable, think creative). Get him a massive weapon, and go to town. This will usually intimidate your opponent into hopelessly blocking for 10-30 seconds (I've timed it). You can extend that time by exhibiting basic skill and breaking their block. The most important thing is to get the first hit and be aggressive from then on.
In racing games... Crash into your opponent. Let the computer win.
In RTS... Make one unimportant base so well defended that your opponent can't get in. everything else can die as far as you care.