Ah, Yanmega. Also known as:
All jokes aside, if you lose some kind of sadistic bet that forces you to add a Bug/Flying type to your competitive team, the joke's on them because GameFreak somehow managed to make a decent competitive Pokemon that has this overused and and terrible type combination. Yanmega still has its faults, but used properly it can make for an effective late-game sweeper.
Pros:
-116 Sp. Attack is impressive, and 95 Speed is usable.
-Two top tier abilities allow it to shore up its Speed or offensive coverage.
-86 HP and Defense aren't terrible for a Bug type.
-It looks badass.
Cons:
-Without Speed Boost, it struggles to outspeed many of its threats, and without Tinted Lens it's liable to get walled by certain types. So it's a matter of pick your poison.
-Suffers from a shallow offensive movepool outside its STAB's, forcing it to rely on moves like Hidden Power and Giga Drain.
-Bug/Flying is still terrible typing offensively and defensively, not to mention the 50% health loss with Stealth Rock.
-58 Sp. Defense is not impressive by any means, and frankly Yanmega has a hard time taking hits in general.
-It looks totally creepy (Cue Misty freak-out).
Set Name: Your Top 'Choice' of Bug/Flying types
Ability: Tinted Lens (alt. Speed Boost)
Item: Choice Specs
Nature: Timid (alt. Modest)
EV's: HP 4, Sp. Attack 252, Speed 252
Movepool:
Bug Buzz
Air Slash
Hidden Power (Ground)
U-Turn (alt. Giga Drain)
Description:
A pretty straightforward choice set that takes full advantage of Tinted Lens. Bug Buzz and Air Slash are your STAB's of choice, the latter of which with any luck may net you a flinch chance and buy you a turn you desperately need. Hidden Power (Ground) offers the best coverage against the Rock/Steel types that 4x resist your STABs, and U-Turn is there so you can bail if you find yourself faced against a target you're ill-suited to take out.
Alternatively, you could opt to run Speed Boost over Tinted Lens to get the speed you really need at the cost of STAB coverage. The only real changes you would have to make to this set is to consider swapping your nature to Modest for the extra power, or replacing U-Turn with Giga Drain to compensate for the lack of coverage.
Set Name: Primeval Dragonfly
Ability: Speed Boost
Item: Life Orb
Nature: Modest
EV's: HP 4, Sp. Attack 252, Speed 252
Movepool:
Bug Buzz
Air Slash
Hidden Power (Ground)/Giga Drain
Protect
Description:
This set sacrifices the power of the choice set for a Life Orb, allowing greater freedom offensively thus enabling Yanmega to swap out less (Thanks a lot Stealth Rock). Second verse same as the first Bug Buzz and Air Slash are for STAB, Hidden Power (Ground) for coverage, though Giga Drain has the bonus of dealing better damage against Rock types whilst healing off Life Orb damage. Protect in the final slot allows you to not just scout, but also guarantees a turn for Speed Boost to kick in and outspeed faster threats. This also lets you run a Modest nature without significant sacrifice to your speed.
The Bug/Flying types are not completely useless. So at least give Yanmega some love: