|| UR Peek/X -- Many players tried substituting in Peek to fill the space lost by Gitaxian Probe, often with a combination of countermagic, Vapor Snag, or additional Sleight of Hand in the mainboard. Some have had considerable success with these builds, and they continue to remain viable versions of the deck.
|| UR Noxious/Sleight -- This is a lower utility, higher consistency version of the build I am running. There is nothing inherently wrong with running Sleight of Hand in place of Thought Scour, but most dedicated users have found that the sleight benefit (pun intended) to consistency does not outweigh the value and versatility that Thought Scour brings to the deck.
|| URb Sideboard Black Splash -- This build is pretty similar to the one I am running, albeit with a Watery Grave instead of a Breeding Pool and a killer sideboard Tech. It was developed by Suicide Bloo creator h0lydiva primarily to improve matchup favorability against GBx decks, but also proved to be very strong against decks like Grixis Delver and Death's Shadow variants. The build runs 2-4x Fatal Push, 0-2x Terminate, and 1-2x Chandra, Torch of Defiance all in the sideboard on top of the usual sideboard staples of Blood Moon and an extra Reveler. The mainboard is nearly identical to mine plus or minus 1-2 cards based on personal preference and local meta. This build is probably the most versatile of Suicide Bloo decks, with the ability to transform into variants that are highly tailored for specific matchups, while retaining the ability to be just as explosive as the original archetype when it needs to be. It is not without its faults though, such as extra life loss on average from the land base (and by extension, the requirement that all phyrexian spells be shocked in) and removal cards becoming dead weight once you resolve Blood Moon.
|| URb Snapcaster Black Splash
Since the rise of Shadow Jund and other Death's Shadow varients, the Modern Meta has become increasingly hostile to Bloo. Because of this, some variants are being tested that splash black for sideboard removal techs and run Snapcaster Mage mainboard in place of Revelers, which are moved over to the side. I won't go into this build in much detail here because it is so new, but here is one example for reference.
|| URG Protection -- This build goes full Temur, with up to two (but generally one) Green-producing shock lands and typically a full playset of Blossoming Defense. I have also seen some builds that additionally run 1-2 Vines of Vastwood. This may be a sensible approach for metas that are loaded to the brim with removal, but it necessarily means that the deck can not run Thought Scour (can't risk milling your only -producing land) or Blood Moon, appreciably lowers the number of cantrips in the deck, and slows down the casting of Bedlam Reveler. This significantly impacts the post-board gameplan against a variety of decks, and by extension, alters matchup favorability. This deck type is definitely viable, but differs strategically so much from the core build that it has arguably become a Kiln Fiend aggro deck in its own right, rather than a version of Bloo.
|| URB Tainted Assault -- This build goes full Grixis to support a mainboard playset of Tainted Strike and multiple copies of Assault Strobe, primarily for alternate and additional ways to combo for a single, lethal attack. Like the URG Protection build, this variant differs enough from the Suicide Bloo core to arguably be considered a separate type of Kiln Fiend aggro deck. Although it has some advantages, this build necessarily loses some degree of resiliency and consistency by dropping some of the utility and organizational cards run by most other builds. It has a lot of ways to pull off Turn 3 wins but is especially susceptible to removal and disruption, a trait that can be pretty problematic in the current Modern meta.