--Flash Beryllium, a horrifically butchered port of Go Beryllium!. Basically, it's got crap hit detection, an even more crap scoring system, completely broken powerups that weren't in the original, and only 3 stages as opposed to 9. It's got pretty cool music though.
--Pester, a mediocre shmup which also has crap hit detection, seemingly created by someone with no clue how to design a shmup just dumping the surface elements of DDP: DFK into a blender.
--Arvoesine, a platformer which uses NES-era design flaws as a "style".
--The works of Mrcredsalex, a bunch of "games" created in order to make money by exploiting Kongregate ad revenue sharing.
--I am personally responsible for over 80 bad games. 70 of them can be found occupying pages 2 through 13 of my old YYG account (page 1 has mostly decent games on it):
http://sandbox.yoyogames.com/users/cjfjcjfjc--A Nation of Wind, an RTS which is so fucking complicated and has such an unsatisfactory tutorial that it's completely unplayable.
--Dungeon Ascension, a platformer consisting of short levels strung together in a random order. It's actually kind of fun once you get into it, but it's also super glitchy and incredibly frustrating.
--Advanced Invasion 3, a fangame of Virus Invasion. It's a platformer, also super glitchy, and the boss fights are ridiculously boring and long.