Sushi Sam's San Mateo?
Sushi Sam's is a local favorite of mine. Although the ambiance there is practically non-existent (sticky menus, plastic plates and cups), it's THE spot in San Mateo for fresh fish. I haven't tried the omakase, however some of the seasonal seafood (which is served with the omakase) is fantastic. Try the butterfish or black cod, if they're available.
Sam's is awesome - you are in for a treat. To maximize your experience order off the whiteboard only. The fish is fresh, unusual, and good.
My personal favorites are the cockle shell, butterfish, and copper river salmon (seasonal). Their Anago is the best I have ever had.
Frequently Sam has items flown in from Japan which are also a good bet. I like to bring in my own champagne to augment the fresh fish.
Sam's defintely appeals to the roll enthusiasts and the nigiri sushi purists, though the omakase chef's sampler menu continues to offer that unique fusion-esque experience that is still a winner with his loyal fans. I admit I secretly enjoyed a chili dog (spicy tuna with wakame salad handroll) or Sam's special (shrimp tempura handroll with sweet sauce) in the past and the spider rolls were great to eat to fill you up early in the game to avoid a hefty bill.
On the white board today were 23 items not on the regular menu, and there were easily 3 or 4 more non white board non menu fish. Some were sure fire hits, and some were just ok, but an experience you will not be able to find elsewhere. If you don't care about decor or presentation, the food here can be great, but prices are indeed competitive with those of the upscale places (that do really great presentation).
On the white board today were white salmon, kinemedai (alfonsino), butterfish (which was medai, not ebodai which was what I had in Seattle), fresh sardine (iwashi), kohada (gizzard shad), fresh katuso (bonito) which is tradtionally seared for health reasons but this was purely raw, baby lobster tail, Japanese unagi salt grilled, anago (imported freshwater eel sourced to his contact in Japan who's a retired eel farmer), tai (sea bream, not sure what variety), artic charr (trout?) that was orange flesh like salmon but better, ark shell clam (aoyagi?), toro, amberjack (kanpachi), yellow jack (shima aji I believe), fresh wild black sea bass from Japan (tenin suzuki), fresh (raw) octopus, sanma (pike mackeral), sayori (needlefish from Japan), black cod (gindara) seared with miso sauce and one piece with only kiwi on top, kobe beef (could be domestic wagyu but I remember it was flown in frozen, so it could be real kobe beef, though not spectacular in the past) plus a few more. This list changes every day depending on season, availability. Of course it pays to go on the days he gets in fish shipments (not sure when, didn't ask).
Of course there's also the special ikura, marinated in soy sauce and sake, but the marination is super heavy, strong in both flavors but more so on the sake. Good hard core stuff!
There's also a black board with a reflective surface to the right of the white board. Those are cooked dishes specials. If Sam has anago tempura that night, it is a wonderful rendition not to be missed. Ditto for the wagyu beef sinews stew (known as wagyu suji on the menu) that his wife makes (who is an excellent chef in her own right), this version surpasses many renditions of the HK style Cantonese beef brisket and tendon stew and has a very refreshing tasting broth/soup base that's also supremely addictive. The downside is that the portion is small (snack/appetizer) and for the same price and maybe a few dollars more you could get a nice HK style brisket and tendon clay pot to feed a small family...