Cards you are embarrassed to not have

[TheShop]

I am missing 1 phyrexian metamorph, 1 preordain, 2 sensei tops...sucks cause my local store is sold out of all of it and I just can't bring myself to drop $20 online...

On a side note:  since I sold my collection, I got back in and picked up nearly everything for shops sans power...but am missing several blue duals and my forces again.

[Wagner]

I'm never been a big blue player except for Bomberman, so I'm missing all Preordain, Gush, Merchant Scroll and all such common utility spells. I also have not bought any pack since Time Spiral, so I'm relying on my drafting friends to give me some staples. I just recently acquired my first Acidic Slime for EDH.

[Ten-Ten]

i'm not embarrassed of not owning a certain card but i am embarrassed of not getting them when they are at a low.

Take LED for example, I picked a playset up for $28 as soon as Ravnica came out just in case Dredge became big. Come FutureSight the same guy who sold them to me was looking for his playset of LED's for his Dreadge deck w/Bridge from below. I had to remind him he sold them to me. Very unhappy was he.

I also picked up Bob for $8-12 ea. but at the same time refused to pay $12 for a Wasteland or $50 for U.Sea 

[CHaPuZaS]

Take LED for example, I picked a playset up for $28 as soon as Ravnica came out just in case Dredge became big. Come FutureSight the same guy who sold them to me was looking for his playset of LED's for his Dreadge deck w/Bridge from below. I had to remind him he sold them to me. Very unhappy was he.

I also picked up Bob for $8-12 ea. but at the same time refused to pay $12 for a Wasteland or $50 for U.Sea 

This was the reason why, around mid-2009 I decided to get a playset of every card I might end up playing in Vintage, Legacy or Modern (Sort of overextended in that period), even though I know I won't be ever (or almost never) playing decks like MUD or Dredge. And I mean not just cards being played, but also remotely playable cards. I know Scaled Wurm won't be in any of my decks, but cards like Obsessive Search, Thought Lash, Urza's Bauble or Chandra Nalaar. That way, I have a beautiful collection of cards and get away of future market fluctuations. I even get playsets of most restricted cards in Vintage and Banned cards in Legacy.

At the moment, the only "Cards (I am) embarrassed to not have" in playsets in that pool, consist mainly on extremely overpriced cards from rarer sets (Mostly Ravages of War, Imperial Recruiter, Loyal Retainers and the like) and cards that get through my radar and got really expensive now, such as Candelabra of Tawnos... ¡But that will be solved with time.

[Joblin Velder]

I've had to proxy Flame Rift and Thornweald Archers. Another time I proxied a Doom Blade. I'm awful.

[KingSquee]

I once had to proxy a Dead / Gone for a last-minute substitution at a Blue Bell tournament during my RG Beats days. I was perfectly willing to spend the 25¢ to buy one, even though I had dozens at home. It's just that nobody had them! It was nice tech against the two dominant strategies at the time, Painter and Tinker for (Darksteel) Colossus.

I am also ashamed to admit I own more Splinter Twins (3) than Deceiver Exarchs (1). Guess that cuts me off one of the major pillars of Modern, eh?

[reaperbong]

I lost my Imperial Seal so right now it's the only proxy I would play with. Kind of embarrassing, I hope it turns up one day.

[metalhead666]

I am still missing a Mox Pearl.  Since I started picking up Shops and Power, I have completely pimped out everything I would play in a shop deck [minus 4 Jester's Caps (I only want german ice age or korean 5th ed), 1 korean Null Rod, 2 korean City of Traitors, 4 Pithing Needle (I cannot find Japanese Saviors ones), and 4 Relic of Progenitus (have not been able to find them at a good price)] as well as most cards for blue decks, except duals, fetches, goyfs, bobs, and random cheap cards. 
I do not play with Drains enough to justify owning them and have traded/sold every one Ive ever gotten.  And I cant justify buying Bazaars for dredge cause Id rather play shops in any sanctioned vintage event Id play in.  So its only the Mox Pearl that I am missing and embarrassed about not having.