I've decided to start a series of actual garbage decks and giving you the right inspiration for your own pile of trash cards. Those decks are not supposed to be anyhow viable against Tier 1-1.5 decks, might not even deal with Tier 2 decks. They are supposed for some giggle and fun, and give cards a spotlight to shine (or not). Also ratios can be done however you think works better. Those decks may or may not be consistent, therefore why they're not good.
So first and foremost: why blue? The answer is simple: Yellow and Purple work waaay too good to play with D-Reaper to be considered a trash deck. Green and Black cards do not really have something that looks "fun" to use and Red is also kind of unspectacular. Blue lets me also play Jeri with Jeri. Which means I still have included a playset of Jeri. ? Because of that I've added Leomon (EX2-017) to this deck which replaces ADR-05 Creep Hands (EX2-050). Jeri and T.K. Takaishi (BT8-087) can also give you free draws depending on the situation. Raddle Star (BT6-098) will be your main removal tool to bottom deck pesky digimons. Lanamon (BT12-024) for Hybrid Finish, and that wraps it up.
If you feel like adding different cards in the blue section, go ahead and try out Innocence Blizzard (BT8-098), Ice Wall! (EX1-068), Sourai (EX3-067), Full Metal Blaze (EX4-067), Howling Crusher (BT1-101), Ice Statue (BT11-099) and Tommy Himi (BT7-086).