Not the best or the most flexible ones, just the ones I enjoyed the most. Usually ones with weird interactions or ones that do something special in that specific deck. Basically just stuff I tried out.
I played the monoblue [scryfall]Brain in a Jar[/scryfall] deck for a while. The idea was to sift through the deck casting random instants and sorceries until you hit critical mass in your graveyard and then cast [scryfall]Rise from the Tides[/scryfall]. Alternative way to win was to chain [scryfall]Part the Waterveil[/scryfall]s. It was definitely an interesting deck. I just felt I needed to have another avenue to victory after sideboarding, so I brought in these beauties. Opponents would, of course, cut most removal from their decks, so it was pretty invulnerable. It was also a way to dodge discard. Because [scryfall]Transgress the Mind[/scryfall] was the prevalent discard spell in Standard at the time, I would use something like [scryfall]Nagging Thoughts[/scryfall] to put the targets into the graveyard before giving them legs.
So, I was playing this horrible monored tokens deck in Standard. It’s one of those “please don’t try this at home” things. It was running stuff like [scryfall]Molten Birth[/scryfall], [scryfall]Goblin Rally[/scryfall] and [scryfall]Ogre Battledriver[/scryfall] in it to combo out and kill the opponent. Every once in a while the opponent would stumble and I would just rush them, but sadly, the deck didn’t do much against the prevalent deck of the time: [scryfall]Sphinx’s Revelation[/scryfall] based control decks. So, what to do? [scryfall]Possibility Storm[/scryfall] was the answer. Not a good one, because it costs five and can still be [scryfall]Detention Sphere[/scryfall]d, but on the other hand, they basically couldn’t cast Revelation or counter anything while that thing was on the table.
Four mana 4/4 with flying and haste sounds pretty good. There is a drawback though. Then again, if the removal opponents are running is sorcery speed… What else am I going to do with all that mana in a monored aggro anyhow?
[scryfall]Profaner of the Dead[/scryfall]
The greatest thing about this is that I managed to talk other people into playing it as well. We were playing a Bant tokens deck when [scryfall]Collected Company[/scryfall] was the biggest thing in Standard. Profaner would just decimate that deck. [scryfall]Gideon, Ally of Zendikar[/scryfall] was the one who usually had to take a hit for the team, but I guess that’s sort of his job.
This is my hipster inclusion in the sense “I was Ranger’s Guiling long before [scryfall]Blossoming Defense[/scryfall]”. Now everyone seems to be playing Defense in my LGS, but back in the day catching my opponents off-guard with it was always fun, because no-one expected it. I would generally run maybe one or two only, because they would definitely catch on.