I think we've definitely reached the point where
you could make a viable singleton-style deck
where every spell flickers something in some
form. I'm not sure you would want to, as it'd be
a whole deck with just one half of the combo,
but there's a niche for just about every card
with that effect, and I think you can make a
good argument for one like this which is also a
good defensive card. Gaining card advantage from
comes-into-play abilities and flickering usually
pushes you towards the control end of the
spectrum, and four toughness is significant
compared to a lot of creatures that cost less
than or as much as the Guardian.
The most infamous thing about Felidar Guardian
is that it goes infinite with Saheeli Rai (from
Kaladesh), which is plenty amusing on its own.
The idea with the combo is that you use Saheeli
Rai's -2 to copy Felidar Guardian; use the
copy's “enter-the-battlefield” trigger to
flicker Saheeli Rai, and rinse and repeat until
you can crash a flood of felines into your
opponent. Felidar Guardian also combos with
Kiki-Jiki, functioning as a worse version of
Restoration Angel.
Shenanigans aside, Felidar Guardian is merely
okay; a 1/4 isn't a great body, so you’re mostly
trying to use this for the ability. This is
definitely a constructed plant, but it’s not
bereft of use outside of that.
