All 90 nervous kaomoji here have a sweat drop, and some are shaking. The drop is usually a semicolon. The shake is extra brackets. Tap a face and it is copied. Twenty-five need only a keyboard, (^_^;) among them.
Read the full guide
Pick how nervous, then tap
Tap a tile and that face is copied. The groups run from mild to bad: smiling through it, a blank stare, wide eyes, shaking, then hands that wipe a brow or press together. Search reads the labels: sorry finds eight faces, the deep bow m(_ _;)m among them, and exam finds (；-人-) and (；・_・) 緊張.
What the semicolon is doing
It is a sweat drop. Wikipedia's article on kaomoji calls (-_-;) a generic emoticon for nervousness, and says an apostrophe or a quotation mark can do the same job, the way a drop is drawn in manga: (^_^') and (^_^") are both here. 67 faces use Semicolon, U+003B, and 20 use Fullwidth semicolon, U+FF1B.
Keyboard only keeps the 25 faces made of plain ASCII. ^^; is the shortest, at three characters.
Twelve faces say it in Japanese. Wiktionary gives dokidoki as with a racing heart and hiyaase as cold sweat.
More brackets, more shaking: ((；・_・)) is a shiver and (((；ﾟДﾟ))) is the whole body.
Questions and answers
What does (^_^;) mean?
A smile with a sweat drop on it: nervous, embarrassed, awkward. Wikipedia's list of emoticons files (^_^;) under nervous, embarrassed, troubled and shy, beside (-_-;), (・_・;) and ^^;. All four are on this page.
How do you type a nervous kaomoji on a keyboard?
Open bracket, caret, underscore, caret, semicolon, close bracket: (^_^;). Leave the brackets off for ^_^; or add a second semicolon when things get worse. The Keyboard only chip shows all 25 that need nothing else.
What does m(_ _)m mean?
A bow with both hands on the floor. Wikipedia's list of emoticons gives m(_ _)m as a kowtow for respect or a dogeza for apology. The one here, m(_ _;)m, adds a semicolon, so the apology is sweating as well.
All 90 nervous kaomoji
Smiling through it 18
(^.^;)Dot mouth, tiny and worried
(^^;)No mouth, one drop
(^_^")Quotation mark for two small drops
(^_^')Apostrophe for a small drop
(^_^;)The plain nervous smile, one drop
(^_^;;)Two drops, it is getting worse
(^▽^;)Open grin that went on too long
(^◇^;)Diamond mouth, stiff laugh
(^皿^;)Grin through gritted teeth
(^～^;)Wavy mouth, not sure about this
(´∀`;)Laughing it off, drop by the ear
(•‿•;)Bullet eyes, small smile, one drop
(⁰▿⁰;)Tiny raised zeros for eyes
(⌒_⌒;)Arched eyes, polite panic
(；^ω^)Drop first, soft w mouth
(；・∀・)Drop first, grin stuck in place
(＾_＾；)Every character fullwidth
(￣▽￣;)Flat eyes, forced grin
Show all 90 nervous kaomoji (72 more)
Blank stare, one drop 19
(-.-;)Flat eyes, dot mouth
(-_-;)Flat eyes, one drop, says nothing
(._.;)Looking at the floor
(=_=;)Equals signs for eyes, enduring it
(~_~;)Tilde eyes, worn down by it
(¬_¬;)Looking away, hoping nobody asks
(´・ω・｀;)Worried brows, one drop
(•_•;)Bullet eyes, frozen
(・.・;)Dot eyes, dot mouth
(・_・;)Dot eyes, staring, one drop
(・_・;)?One drop and a question
(・ω・;)Soft w mouth, one drop
(・・;)Dot eyes and no mouth at all
(ーー;)Two long sound marks for eyes
(ㆆ_ㆆ;)Hooded eyes, suspicious and sweating. Borrows ㆆ from Hangul.
(；一_一)The kanji for one, twice, as narrowed eyes
(￣_￣;)Macron eyes, keeping quiet
(o_o;)Round letter eyes, frozen
(ó_ò;)Letter o eyes under worried accents
Wide eyes, wobbly mouths 17
(>_<;)Eyes squeezed shut, one drop
(>﹏<;)Eyes squeezed shut, bracing
(°_°;)Degree signs for eyes, frozen stiff
(°△°;)Triangle mouth, alarmed
(ʘ_ʘ;)Eyes made of a click consonant. Borrows ʘ from IPA Extensions.
(⊙_⊙;)Circled dots for eyes, staring
(⊙﹏⊙;)Wobbly mouth, eyes wide
(◎_◎;)Bullseye eyes, one drop
(⚆_⚆;)Both eyes darting to the right
(・﹏・;)Wobbly mouth, dot eyes
(；ﾟДﾟ)Drop first, mouth wide open
(；￣Д￣)Flat eyes, jaw hanging open
(ﾟロﾟ;)Square katakana mouth, aghast
Σ(°△°;)A jolt: capital sigma for the shock
Σ(￣□￣;)Jolt, square mouth, flat eyes
(0_0;)Zeros for eyes, one drop
(°o°;)Round mouth, caught out
Shaking, flailing, running 9
(((-_-;)))Flat eyes, shaking anyway
(((^_^;)))Still smiling, visibly shaking
(((⊙﹏⊙;)))Wide eyes, wobbly mouth, shaking
(((；ﾟДﾟ)))Three brackets a side, shaking all over
((；・_・))Two brackets a side, a small shiver
(／;°ロ°)／Arms up, looking right for a way out
ε=ε=┌(；・_・)┘Running off, two puffs of dust behind
ヽ(；ﾟДﾟ)ﾉBoth arms flailing, mouth open
＼(°ロ°;＼)Arms up, looking left for a way out
Wiping, scratching, bowing 8
(^^;ゞHead scratch, no closing bracket
(^_^;)ゞHand to the back of the head
(；-人-)Palms together, waiting for the result
(；>人<)Eyes shut, palms pressed together
σ(^_^;)Pointing at itself: who, me
(；^_^ACapital A for a hand wiping the brow
f(^_^;)Letter f for a finger scratching the cheek
m(_ _;)mDeep bow, hands on the floor, one drop
With a Japanese word 12
(((；ﾟДﾟ))) ガクガクGakugaku, trembling with fear or cold