It's always interesting to see how lead singles fair in the first week of sales. I'll start the OP off with a few, and if you have any additional ones to add, please post as a comment and I'll update as necessary. Please have receipts. 
AVRIL LAVIGNE
Complicated (lead single from 'Let Go') - ???
Don't Tell Me (lead single from 'Under My Skin') - ???
Girlfriend (lead single from 'The Best Damn Thing') -
122,000
What The Hell (lead single from 'Goodbye Lullaby') -
163,000
BEYONCE
Crazy In Love (featuring Jay-Z) (lead single from 'Dangerously In Love') - ???
Check On It (lead single/track for 'The Pink Panther') - ???
Deja Vu (featuring Jay-Z) (lead single from 'B-Day) -
75,000
If I Were A Boy / Single Ladies (Put a Ring On It) (lead singles from 'I Am... Sasha Fierce') -
190,000 /
204,000
Run The World (Girls) (lead single from '4') -
77,000
BRITNEY SPEARS
...Baby One More Time (lead single from '...Baby One More Time') - ???
Oops!... I Did It Again (lead single from 'Oops!... I Did It Again) - ???
I'm A Slave 4 U (lead single from 'Britney') - ???
Me Against The Music (featuring Madonna) (lead single from 'In The Zone') - ???
Gimme More (lead single from 'Blackout') -
179,000
Womanizer (lead single from 'Circus') -
286,000
3 (lead single from 'The Singles Collection') -
255,000
Hold It Against Me (lead single from 'Femme Fatale') -
411,000
FLO RIDA
Low (featuring T-Pain) (lead single from 'Mail On Sunday') - ???
Right Round (lead single from R.O.O.T.S.) -
636,000
Club Can't Handle Me (featuring David Guetta) (lead single from 'Only One Flo: Pt 1') - ???
Good Feeling (lead single from 'Wild Ones') - ???
GAGA
Just Dance (featuring Colby ODonis) (lead single from 'The Fame') - ???
Bad Romance (lead single from 'The Fame Monster') -
142,000
Born This Way (lead single from 'Born This Way') -
448,000
JUSTIN TIMBERLAKE
Sexyback (featuring Timbaland) (lead single from 'FutureSex/LoveSounds') -
250,000
KATY PERRY
I Kissed A Girl (lead single from 'One Of The Boys') - ???
California Gurls (featuring Snoop Dogg) (lead single from 'Teenage Dream') -
294,000
Part Of Me (lead single from 'Teenage Dream: The Complete Confection') -
411,000
KELLY CLARKSON
Miss Independent (lead single from 'Thankful') - ???
Breakaway (lead single from 'Breakaway') - ???
Never Again (lead single from 'My December') -
100,000
My Life Would Suck Without You (lead single from 'All I Ever Wanted') -
280,000
Mr Know It All (lead single from 'Stronger') -
107,000
KE$HA
Tik Tok (lead single from 'Animal') - ???
We R Who We R (lead single from 'Cannibal') -
280,000
Die Young (lead single from 'Warrior') -
188,000
MADONNA
4 Minutes (featuring Justin Timberlake) (lead single from 'Hard Candy') -
217,000
Give Me All Your Luvin' (featuring Nicki Minaj and M.I.A. (lead single from 'MDNA') -
115,000
MAROON 5
This Love (lead single from 'Songs About Jane') - ???
Makes Me Wonder (lead single from 'It Won't Be Soon Before Long') -
244,000
Misery (lead single from 'Hands All Over') - ???
Payphone (featuring Wiz Khalifa) (lead single from 'Overexposed') -
493,000
P!NK
There You Go (lead single from 'Can't Take Me Home') - ???
Get The Party Started (lead single from 'Missundaztood) - ???
Feel Good Time (lead single from 'Try This') - ???
Stupid Girls (lead single from 'I'm Not Dead') - ???
So What (lead single from 'Funhouse') - ???
Raise Your Glass (lead single from 'The Greatest Hits... So Far!) - ???
Blow Me (One Last Kiss) (lead single from 'The Truth About Love') - ???
RIHANNA
Pon De Replay (lead single from 'Music Of The Sun') - ???
S.O.S. (lead single from 'A Girl Like Me') -
170,000
Umbrella (featuring Jay-Z) (lead single from 'Good Girl Gone Bad') -
277,000
Take A Bow (lead single from 'Good Girl Gone Bad: Reloaded') -
267,000
Russian Roulette (lead single from 'Rated R') - ???
Only Girl (In The World) (lead single from 'Loud') -
249,000
We Found Love (featuring Calvin Harris) (lead single from 'Talk That Talk') -
117,000
Diamonds (lead single from '???') -
133,000
TAYLOR SWIFT
Tim McGraw (lead single from 'Taylor Swift') - ???
Love Story (lead single from 'Fearless') -
97,000
Mine (lead single from 'Speak Now') -
297,000
Eyes Open (lead single/track from 'The Hunger Games') -
176,000
We Are Never Ever Getting Back Together (lead single from 'Red') -
623,000
TIMBALAND
Give It To Me (featuring Nelly Furtado & Justin Timberlake) (lead single from 'Shock Value') -
248,000
