Skyward Spider
The conditional flying is the pivot the whole card turns on, because it converts a plain 2/2 into a payoff for something an equipment or auras deck was doing anyway. Strap on a sword, staple an Aura, drop a +1/+1 counter: the instant the body is modified it takes to the air and starts connecting for the extra value those attachments carry. Left bare it stays grounded, which is the honest cost of the design; the card wants to be dressed up, and offers nothing evasive until it is. Ward 
is the piece that makes the investment safe. Suiting up a two-drop always risks the attached Auras evaporating to a cheap removal spell, and the two-mana tax buys enough of a window that opponents often cannot answer it on curve without falling behind. The hybrid cost widens where it fits, too: it can anchor a mono-white auras build or a mono-blue tempo shell as readily as the two-color pairing it nominally belongs to, because either single color pays for it outright.
Rules text
(Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays .)
This creature has flying as long as it's modified. (Equipment, Auras you control, and counters are modifications.)